JWT in ASP.NET Core
JWT (JSON web token) has become more and more popular in web development. It is an open standard which allows transmitting data between parties as a JSON object in a secure and compact way. The data transmitting using JWT between parties are digitally signed so that it can be easily verified and trusted.

In this article, we will learn how to setup JWT with ASP.NET core web application. We can create an application using Visual Studio or using CLI (Command Line Interface).

    dotnet new webapi -n JWTAuthentication   

Above command will create an ASP.NET Web API project with the name "JWTAuthentication" in the current folder.
 
The first step is to configure JWT based authentication in our project. To do this, we need to register a JWT authentication schema by using "AddAuthentication" method and specifying JwtBearerDefaults.AuthenticationScheme. Here, we configure the authentication schema with JWT bearer options.
    public void ConfigureServices(IServiceCollection services)    
    {    
        services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)    
        .AddJwtBearer(options =>    
        {    
            options.TokenValidationParameters = new TokenValidationParameters    
            {    
                ValidateIssuer = true,    
                ValidateAudience = true,    
                ValidateLifetime = true,    
                ValidateIssuerSigningKey = true,    
                ValidIssuer = Configuration["Jwt:Issuer"],    
                ValidAudience = Configuration["Jwt:Issuer"],    
                IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"]))    
            };    
        });    
        services.AddMvc();    
    }   

In this example, we have specified which parameters must be taken into account to consider JWT as valid. As per our code,  the following items consider a token valid:

    Validate the server (ValidateIssuer = true) that generates the token.
    Validate the recipient of the token is authorized to receive (ValidateAudience = true)
    Check if the token is not expired and the signing key of the issuer is valid (ValidateLifetime = true)
    Validate signature of the token (ValidateIssuerSigningKey = true)
    Additionally, we specify the values for the issuer, audience, signing key. In this example, I have stored these values in appsettings.json file.

AppSetting.Json

    {    
      "Jwt": {    
        "Key": "ThisismySecretKey",    
        "Issuer": "Test.com"    
      }    
    }   

The above-mentioned steps are used to configure a JWT based authentication service. The next step is to make the authentication service is available to the application. To do this, we need to call app.UseAuthentication() method in the Configure method of startup class. The UseAuthentication method is called before UseMvc method.

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)    
    {    
        app.UseAuthentication();    
        app.UseMvc();    
    }

Generate JSON Web Token
I have created a LoginController and Login method within this controller, which is responsible to generate the JWT. I have marked this method with the AllowAnonymous attribute to bypass the authentication. This method expects the Usermodel object for Username and Password.
 
I have created the "AuthenticateUser" method, which is responsible to validate the user credential and returns to the UserModel. For demo purposes, I have returned the hardcode model if the username is "Peter". If the "AuthenticateUser" method returns the user model, API generates the new token by using the "GenerateJSONWebToken" method.
 
Here, I have created a JWT using the JwtSecurityToken class. I have created an object of this class by passing some parameters to the constructor such as issuer, audience, expiration, and signature.
 
Finally, JwtSecurityTokenHandler.WriteToken method is used to generate the JWT. This method expects an object of the JwtSecurityToken class.
    using Microsoft.AspNetCore.Authorization;    
    using Microsoft.AspNetCore.Mvc;    
    using Microsoft.Extensions.Configuration;    
    using Microsoft.IdentityModel.Tokens;    
    using System;    
    using System.IdentityModel.Tokens.Jwt;    
    using System.Security.Claims;    
    using System.Text;    
        
    namespace JWTAuthentication.Controllers    
    {    
        [Route("api/[controller]")]    
        [ApiController]    
        public class LoginController : Controller    
        {    
            private IConfiguration _config;    
        
            public LoginController(IConfiguration config)    
            {    
                _config = config;    
            }    
            [AllowAnonymous]    
            [HttpPost]    
            public IActionResult Login([FromBody]UserModel login)    
            {    
                IActionResult response = Unauthorized();    
                var user = AuthenticateUser(login);    
        
                if (user != null)    
                {    
                    var tokenString = GenerateJSONWebToken(user);    
                    response = Ok(new { token = tokenString });    
                }    
        
                return response;    
            }    
        
            private string GenerateJSONWebToken(UserModel userInfo)    
            {    
                var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_config["Jwt:Key"]));    
                var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256);    
        
                var token = new JwtSecurityToken(_config["Jwt:Issuer"],    
                  _config["Jwt:Issuer"],    
                  null,    
                  expires: DateTime.Now.AddMinutes(120),    
                  signingCredentials: credentials);    
        
                return new JwtSecurityTokenHandler().WriteToken(token);    
            }    
        
            private UserModel AuthenticateUser(UserModel login)    
            {    
                UserModel user = null;    
        
                //Validate the User Credentials    
                //Demo Purpose, I have Passed HardCoded User Information    
                if (login.Username == "Peter")    
                {    
                    user = new UserModel { Username = "Peter", EmailAddress = "[email protected]" };    
                }    
                return user;    
            }    
        }    
    }   

Once, we have enabled the JWT based authentication, I have created a simple Web API method that returns a list of value strings when invoked with an HTTP GET request. Here, I have marked this method with the authorize attribute, so that this endpoint will trigger the validation check of the token passed with an HTTP request.
 
If we call this method without a token, we will get 401 (UnAuthorizedAccess) HTTP status code as a response. If we want to bypass the authentication for any method, we can mark that method with the AllowAnonymous attribute.
 
To test the created Web API, I am Using Fiddler. First, I have requested to "API/login" method to generate the token. I have passed the following JSON in the request body.
    {"username": "Peter", "password": "password"}

As a response, we will get the JSON like the following,
    {    
        "token" : "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJKaWduZXNoIFRyaXZlZGkiLCJlbWFpbCI6InRlc3QuYnRlc3RAZ21haWwuY29tIiwiRGF0ZU9mSm9pbmciOiIwMDAxLTAxLTAxIiwianRpIjoiYzJkNTZjNzQtZTc3Yy00ZmUxLTgyYzAtMzlhYjhmNzFmYzUzIiwiZXhwIjoxNTMyMzU2NjY5LCJpc3MiOiJUZXN0LmNvbSIsImF1ZCI6IlRlc3QuY29tIn0.8hwQ3H9V8mdNYrFZSjbCpWSyR1CNyDYHcGf6GqqCGnY"    
    }  
Now, we will try to get the list of values by passing this token into the authentication HTTP header. Following is my Action method definition.
    [HttpGet]    
    [Authorize]    
    public ActionResult<IEnumerable<string>> Get()    
    {    
        return new string[] { "value1", "value2", "value3", "value4", "value5" };    
    }  

    Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJKaWduZXNoIFRyaXZlZGkiLCJlbWFpbCI6InRlc3QuYnRlc3RAZ21haWwuY29tIiwiRGF0ZU9mSm9pbmciOiIwMDAxLTAxLTAxIiwianRpIjoiYzJkNTZjNzQtZTc3Yy00ZmUxLTgyYzAtMzlhYjhmNzFmYzUzIiwiZXhwIjoxNTMyMzU2NjY5LCJpc3MiOiJUZXN0LmNvbSIsImF1ZCI6IlRlc3QuY29tIn0.8hwQ3H9V8mdNYrFZSjbCpWSyR1CNyDYHcGf6GqqCGnY 

Handle Claims with JWT
Claims are data contained by the token. They are information about the user which helps us to authorize access to a resource. They could be Username, email address, role, or any other information. We can add claims information to the JWT so that they are available when checking for authorization.
 
In the above example, if we want to pass the claims to our token then the claim information needs to add GenerateJSONWebToken method of Login controller. In the following example, I have added a username, email address, and date of joining as claimed into the token.

    private string GenerateJSONWebToken(UserModel userInfo)    
    {    
        var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_config["Jwt:Key"]));    
        var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256);    
        
        var claims = new[] {    
            new Claim(JwtRegisteredClaimNames.Sub, userInfo.Username),    
            new Claim(JwtRegisteredClaimNames.Email, userInfo.EmailAddress),    
            new Claim("DateOfJoing", userInfo.DateOfJoing.ToString("yyyy-MM-dd")),    
            new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString())    
        };    
        
        var token = new JwtSecurityToken(_config["Jwt:Issuer"],    
            _config["Jwt:Issuer"],    
            claims,    
            expires: DateTime.Now.AddMinutes(120),    
            signingCredentials: credentials);    
        
        return new JwtSecurityTokenHandler().WriteToken(token);    
    }   

The claims are an array of key-value pair. The keys may be values of a JwtRegisteredClaimNames structure (it provides names for public standardized claims) or custom name (such as DateOfJoining in above example).
 
This claims can be used to filter the data. In the following example, I have to change the list of values if the user spends more than 5 years with the company.
    [HttpGet]    
    [Authorize]    
    public ActionResult<IEnumerable<string>> Get()    
    {    
        var currentUser = HttpContext.User;    
        int spendingTimeWithCompany = 0;    
        
        if (currentUser.HasClaim(c => c.Type == "DateOfJoing"))    
        {    
            DateTime date = DateTime.Parse(currentUser.Claims.FirstOrDefault(c => c.Type == "DateOfJoing").Value);    
            spendingTimeWithCompany = DateTime.Today.Year - date.Year;    
        }    
        
        if(spendingTimeWithCompany > 5)    
        {    
            return new string[] { "High Time1", "High Time2", "High Time3", "High Time4", "High Time5" };    
        }    
        else    
        {    
            return new string[] { "value1", "value2", "value3", "value4", "value5" };    
        }    
    }   

JWT is very famous in web development. It is an open standard that allows transmitting data between parties as a JSON object in a secure and compact way. In this article, we will learn how to generate and use JWT with ASP.NET core application.

This article provides some guidelines on how to use AutoMapper in C#.
We have come across a lot of situations when we need to copy data from one object to another. Normally, we follow the below mentioned approach to achieve this. Let’s say we have two classes declared as below,

First Class:
    public class UserObject  
       {  
           public int Id;  
           public string Name;  
           public string Address;  
       }  

Second Class:
    public class UserAnotherObject  
    {  
        public int Id;  
        public string Name;  
        public string Address;  
    }  

Now, if an object of the first class have some data in it and we want to copy that data to an object of the second class, we would be using the following approach for this:
    UserObject uObj = new UserObject();                         //an object of First Class  
               UserAnotherObject uAnotherObj = new UserAnotherObject();    //an object of Second   
      
               uAnotherObj.Id = uObj.Id;  
               uAnotherObj.Name = uObj.Name;  
               uAnotherObj.Address = uObj.Address;   

This is undoubtedly a tedious and repetitive task in case the object has a lot of properties.

Now, to overcome this task we can use a Nuget Package called the Auto-Mapper. Its working is quite simple to explain, in that it creates copy of one object into another but a bit automatically on the basis of Datatypes and names of the properties.

In order to use AutoMapper we would have to install it first from the Nuget Package Manager as pictorially explained below:

Step 1: Go to Manage NuGet Packages.. option in the project.
 

Step 2: Search and install AutoMapper to your project.

Step 3: Include the required Library on the page.
    using AutoMapper.Mappers;   

Now that this been done, we create a Mapper between the UserObject class and UserAnotherObject class. This will be done using the following line.

    AutoMapper.Mapper.CreateMap<UserObject, UserAnotherObject>();   

After creating this Mapper, let’s put some data into the object of the class UserObject that we made above,
    uObj.Id = 123;  
    uObj.Name = "Peter";  
    uObj.Address = "London";  

Now that we have the data, let’s copy the data from the object of UserObject class into the object of class UserAnotherObject using the AutoMapper that we just created above.
    uAnotherObj = AutoMapper.Mapper.Map<UserAnotherObject>(uObj);   

This copies the complete data from the uObj object to uAnotherObj object.

Note:
We need to keep it in mind that Auto Mapper copies data to properties in the target object with the same name as the properties name in the source object. The name should be the same but NOT CASE-SENSITIVE i.e. the name in source object can be “id” and that in the target object can be “ID”.

In this tutorial, I will show you how to work with structured logging in ASP.NET Core and Serilog. Let's start with logging, add NuGet packages:
    Serilog.AspNetCore
    Serilog.Sinks.Literate
    Serilog.Sinks.Seq

In Program.cs, configure Serilog using its LoggerConfiguration class and storing an instance of ILogger (returned by CreateLogger) in Serilog’s static Log class.
    public static void Main(string[] args)  
          {  
              Log.Logger = new LoggerConfiguration()  
                          .WriteTo.LiterateConsole()  
                          .CreateLogger();  
      
             BuildWebHost(args).Run();  
          }  
      
          public static IWebHost BuildWebHost(string[] args) =>  
              WebHost.CreateDefaultBuilder(args)  
                  .UseStartup<Startup>()  
                  .UseSerilog()  
                  .Build();  

Using the ILogger is the same process as described in our previous post, however, with Serilog we can do structured logging.
    public async Task Invoke(HttpContext context)  
        {  
            var message = new  
            {  
                GreetingTo = "James Bond",  
                GreetingTime = "Morning",  
                GreetingType = "Good"  
            };  
            this.logger.LogInformation("Inoke executing {@message}", message);  
      
            await context.Response.WriteAsync("Hello Logging!");  
      
            this.logger.LogInformation(  
                "Inoke executed by {developer} at {time}", "Tahir", DateTime.Now);  
        }

Running the application will show messages in Console window.

Structured logging is a technique to include semantic information as part of the messages being logged. This helps ‘machine readability’ of these messages and tools can be written to analyze raw log messages and produce interesting information.

Serilog uses message template, similar to string.Format() in .NET. Few interesting aspects of template syntax are,
    Use {} to enclose property names e.g. {developer} in above solution. These will be stored as metadata and can be queried using structured data storage (e.g. Seq, Azure).
    Use @ to preserve object structure e.g. in solution above the anonymous object is serialized into JSON representation.

Enrichers
In Serilog, enrichers are used to attach information to every log event that can then be used by structured data storage (e.g. Seq, Azure) for viewing and filtering. A simple way to do this is by using .Enrich.WithProperty() when configuring Serilog,
    Log.Logger = new LoggerConfiguration()  
                               .Enrich.WithProperty("ApiVersion", "1.2.5000")  
                               .WriteTo.LiterateConsole()  
                               .CreateLogger();  
As we saw in the previous post, a category can be attached to the logged messages, which normally is the fully qualified name of the class. This information could be used by structured data storage (e.g. Seq, Azure). Serilog provides this mechanism by attaching Context via ForContext() method,
    Log.Logger = new LoggerConfiguration()  
                        .Enrich.WithProperty("ApiVersion", "1.2.5000")  
                        .WriteTo.LiterateConsole()  
                        .CreateLogger()  
                        .ForContext<HelloLoggingMiddleware>();  

Sinks
Sinks in Serilog refer to destination of log messages e.g. file, database or console (in our example). There are several sinks available (refer to link below). I’ll use Seq as an example sink to show how all the metadata we’ve added is available in a structured storage,
    Log.Logger = new LoggerConfiguration()  
                              .Enrich.WithProperty("ApiVersion", "1.2.5000")  
                              .WriteTo.LiterateConsole()  
                              .WriteTo.Seq("http://localhost:5341")  
                              .CreateLogger()  
                              .ForContext<HelloLoggingMiddleware>(); 

Notice how data we added via enricher, context and custom object appears as key/value pairs. This can now be used for filtering data and creating dashboards within Seq.

In this article, I give a brief introduction to writing testable code. Although I have described and used samples in the context of .NET, the high-level principles of writing testable code applies to most of the programming language.  
 
What is Testable Code?
Testable code refers to the loosely coupled code where code does not directly depend on internal/external dependencies, so we can easily replace the real dependencies (sometimes referred to as real service) with mock services in test cases. For example, if my code calls a method GetProductInfo() which is connecting to a real database, fetching the product information, and returning to the main method. To test my main method functionality without actually connecting to the real database, I can write a test that uses a mock service to get product data.
 
While it might seem a little confusing at this point, it is actually very simple when you see a working example of it.
 
Why is it important to write testable code?
Writing testable code is crucial, as it helps you to identify and resolve the potential problems/ bugs in the early development stage instead of getting issues in UAT or production when working with real services. Also, testing the fake services is fast compared to testing real services. For example, connecting to a real database is more time consuming than testing with fake data in mock service.
 
How to write testable code
Writing testable code is all about dependency management. If we are writing code using the SOLID principles, then our code will already be loosely coupled and in compliance with testing standards. While writing testable code, our main objective is to identify the dependencies and moving the instantiation of those dependencies outside of our code. When we create an object of the class using a new keyword inside the current class, then this class directly depends on the class whose object we are creating. For example, in the below code ProcessProduct class creating the object of DBService class. Hence DBService class is the dependency and ProcessProduct class depends directly on DBService.
    class Product  
        {  
            public int Id { get; set; }  
            public string Name { get; set; }  
            public string Category { get; set; }  
            public float Price { get; set; }  
      
        }  
        class ProcessProduct  
        {  
            public void DisplayProduct()  
            {  
                DBService dbService = new DBService();  
                var product = dBService.getProduct();  
                Console.WriteLine($" Product Name: { product.Name } Category: { product.Category } Price: { product.Price }");  
            }  
              
        }  
      
        class DBService  
        {  
            public Product getProduct() {  
                throw new NotImplementedException("Get product from database");  
            }  
        }  

To make this code loosely coupled, we will use a very popular design pattern called dependency injection. There are several ways to implement dependency injection which is itself a very wide topic. So to keep this article simple, I will use one of the ways to implement dependency injection-  Dependency injection using Constructor.
 
In this method, instead of creating the object of DBService inside ProcessProduct, we will inject the object through the constructor of the dependent class and save it in a private variable as shown in the below code:
    class Product  
    {  
        public int Id { get; set; }  
        public string Name { get; set; }  
        public string Category { get; set; }  
        public float Price { get; set; }  
      
    }  
    class ProcessProduct  
    {  
        private IDBservice _dbService;  
      
        public ProcessProduct(IDBservice dbService)  
        {  
            _dbService = dbService;  
        }  
        public void DisplayProduct()  
        {  
            var product = _dbService.getProduct();  
            Console.WriteLine($" Product Name: { product.Name } Category: { product.Category } Price: { product.Price }");  
        }  
          
    }  
      
    interface IDBservice {  
         Product getProduct();  
    }  
      
    class DBService : IDBservice  
    {  
        public Product getProduct() {  
            throw new NotImplementedException("Get product from database");  
        }  
    }  

We have also created an interface IDBService in the above example and declared the object of DBService using this interface. By using this interface, we allow any class’object that implements the IDBService interface to inject through the constructor.
 
Below is an example of passing a mock class object for testing.
    class ProcessProduct  
        {  
            private IDBservice _dbService;  
      
            public ProcessProduct(IDBservice dbService)  
            {  
                _dbService = dbService;  
            }  
            public void DisplayProduct()  
            {  
                var product = _dbService.getProduct();  
                Console.WriteLine($" Product Name: { product.Name } Category: { product.Category } Price:  { product.Price }");  
            }  
      
        }  
      
        interface IDBservice {  
            Product getProduct();  
        }  
      
        class MockDBService : IDBservice  
        {  
            public Product getProduct()  
            {  
                return new Product()  
                {  
                    Id = 2124,  
                    Name = "Eggs",  
                    Category = "Food",  
                    Price = 2.23m  
                };  
      
            }  
      
        }  
      
        class TestProcessProduct  
        {  
            void Test()  
            {  
                ProcessProduct processProduct = new ProcessProduct(new MockDBService());  
                processProduct.DisplayProduct();  
            }  
        }  

In this example, we want to test the ProcessProduct class to display product information without actually connecting to the real database. To achieve this, instead of injecting the DBService class object we are injecting the MockDBService class object. And because of dependency injection, we do not need to do any changes in the ProcessProduct class. Hence, this code is loosely coupled and testable.

Sometimes you want to remove tags from HTML and get only plain text. In general, this is simple task but there are few drawbacks in some scenarios. The simplest solution is to just remove all tags from given HTML without any formatting.

You can do it with code like this:

[ C# ]

public string RemoveHTMLTags(string HTMLCode)
{
 return System.Text.RegularExpressions.Regex.Replace(
   HTMLCode, "<[^>]*>", "");
}

[ VB.NET ]

Public Function RemoveHTMLTags(ByVal HTMLCode As String) As String
 Return System.Text.RegularExpressions.Regex.Replace( _
   HTMLCode, "<[^>]*>", "")
End Function

Better HTML to plain text conversion\

Example above removes any tag from HTML. This is good enough in some scenarios, but there are some issues too:

- Text inside HEAD tag will be visible too
- Empty spaces &nbsp; and new lines <br /> or paragraph <p> will be lost
- Unwanted empty spaces that are invisible in HTML will show in plain text, and that will distract text even more
- Special characters like &amp; or &copy etc. will not be translated etc

To solve all these problems, you need a little more processing of input HTML. Next function will provide better HTML to text conversion:

[ C# ]

// This function converts HTML code to plain text
// Any step is commented to explain it better
// You can change or remove unnecessary parts to suite your needs

public string HTMLToText(string HTMLCode)
{
 // Remove new lines since they are not visible in HTML
 HTMLCode = HTMLCode.Replace("\n", " ");
 
 // Remove tab spaces
 HTMLCode = HTMLCode.Replace("\t", " ");
 
 // Remove multiple white spaces from HTML
 HTMLCode = Regex.Replace(HTMLCode, "\\s+", " ");
 
 // Remove HEAD tag
 HTMLCode = Regex.Replace(HTMLCode, "<head.*?</head>", ""
                     , RegexOptions.IgnoreCase | RegexOptions.Singleline);
 
 // Remove any JavaScript
 HTMLCode = Regex.Replace(HTMLCode, "<script.*?</script>", ""
   , RegexOptions.IgnoreCase | RegexOptions.Singleline);
 
 // Replace special characters like &, <, >, " etc.
 StringBuilder sbHTML = new StringBuilder(HTMLCode);

// Note: There are many more special characters, these are just
// most common. You can add new characters in this arrays if needed
 string[] OldWords = {"&nbsp;", "&amp;", "&quot;", "&lt;",
   "&gt;", "&reg;", "&copy;", "&bull;", "&trade;"};
 string[] NewWords = {" ", "&", "\"", "<", ">", "®", "©", "•", "â„¢"};
 for(int i = 0; i < OldWords.Length; i++)
 {
   sbHTML.Replace(OldWords[i], NewWords[i]);
 }
 
 // Check if there are line breaks (<br>) or paragraph (<p>)
 sbHTML.Replace("<br>", "\n<br>");
 sbHTML.Replace("<br ", "\n<br ");
 sbHTML.Replace("<p ", "\n<p ");
 
 // Finally, remove all HTML tags and return plain text
 return System.Text.RegularExpressions.Regex.Replace(
   sbHTML.ToString(), "<[^>]*>", "");
}

[ VB.NET ]

' This function converts HTML code to plain text
' Any step is commented to explain it better
' You can change or remove unnecessary parts to suite your needs

Public Function HTMLToText(ByVal HTMLCode As String) As String
 ' Remove new lines since they are not visible in HTML
 HTMLCode = HTMLCode.Replace("\n", " ")
 
 ' Remove tab spaces
 HTMLCode = HTMLCode.Replace("\t", " ")
 
 ' Remove multiple white spaces from HTML
 HTMLCode = Regex.Replace(HTMLCode, "\\s+", "  ")
 
 ' Remove HEAD tag
 HTMLCode = Regex.Replace(HTMLCode, "<head.*?</head>", "" _
   , RegexOptions.IgnoreCase Or RegexOptions.Singleline)
 
 ' Remove any JavaScript
 HTMLCode = Regex.Replace(HTMLCode, "<script.*?</script>", "" _
   , RegexOptions.IgnoreCase Or RegexOptions.Singleline)
 
 ' Replace special characters like &, <, >, " etc.
 Dim sbHTML As StringBuilder = New StringBuilder(HTMLCode)

 ' Note: There are many more special characters, these are just
 ' most common. You can add new characters in this arrays if needed

 Dim OldWords() As String = {"&nbsp;", "&amp;", "&quot;", "&lt;", _
    "&gt;", "&reg;", "&copy;", "&bull;", "&trade;"}
 Dim NewWords() As String = {" ", "&", """", "<", ">", "®", "©", "•", "â„¢"}
 For i As Integer = 0 To i < OldWords.Length
   sbHTML.Replace(OldWords(i), NewWords(i))
 Next i
 
 ' Check if there are line breaks (<br>) or paragraph (<p>)
 sbHTML.Replace("<br>", "\n<br>")
 sbHTML.Replace("<br ", "\n<br ")
 sbHTML.Replace("<p ", "\n<p ")
 
 ' Finally, remove all HTML tags and return plain text
 Return System.Text.RegularExpressions.Regex.Replace( _
    sbHTML.ToString(), "<[^>]*>", "")
End Function

HTML to plain text ASP.NET example

Now, you can build an example that convert HTML to plain text. Create new web page with one Button control and two TextBox controls, like on image bellow:

First TextBox control ID will be tbHTML and second TextBox control ID set to tbPlainText. On button's click write this code:

[ C# ]

protected void btnTextToHTML_Click(object sender, EventArgs e)
{
 tbPlainText.Text = HTMLToText(tbHTML.Text);
}

[ VB.NET ]

Protected Sub btnTextToHTML_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnTextToHTML.Click
 tbPlainText.Text = HTMLToText(tbHTML.Text)
End Sub

Please note that HTML is considered as dangerous input. To make this example works you need to add ValidateRequest="false" part to @Page directive. Otherwise, you'll get an error "A potentially dangerous Request.Form value was detected from the client...)" like on next image.

When you set ValidateRequest parameter to false, you can run an example. Place some HTML code to tbHTML TextBox control and click on Button. Plain text will be extracted from given HTML and shown in tbPlainText.

As you see, there are few different options when converting HTML to plain text. Depending of your needs you can only remove tags or provide additional formatting. Suggested HTMLToText function is not perfect. You can make it better if you add all symbols or add line breaks for new table rows, or add tab spaces for evey new table cell etc. Be aware that with every new option included this function becomes slower. If you overdo the conversion could be unsatisfactory, especially if you have large HTML files. Happy coding!

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Distributed computing is an integral part of almost every software development. Before .Net Remoting, DCOM was the most used method of developing distributed application on Microsoft platform. Because of object oriented architecture, .NET Remoting replaces DCOM as .Net framework replaces COM.
 
Benefits of Distributed Application Development
 
Fault Tolerance: Fault tolerance means that a system should be resilient when failures within the system occur.
 
Scalability: Scalability is the ability of a system to handle increased load with only an incremental change in performance.
 
Administration: Managing the system from one place.
 
In brief, .NET remoting is an architecture which enables communication between different application domains or processes using different transportation protocols, serialization formats, object lifetime schemes, and modes of object creation. Remote means any object which executes outside the application domain. The two processes can exist on the same computer or on two computers connected by a LAN or the Internet. This is called marshalling (This is the process of passing parameters from one context to another.), and there are two basic ways to marshal an object:
 
Marshal by value: the server creates a copy of the object passes the copy to the client.
 
Marshal by reference: the client creates a proxy for the object and then uses the proxy to access the object.
 
Comparison between .NET Remoting and Web services

Architecture
Remote objects are accessed thro channels. Channels are Transport protocols for passing the messages between Remote objects. A channel is an object that makes communication between a client and a remote object, across app domain boundaries. The .NET Framework implements two default channel classes, as follows:
 
HttpChannel: Implements a channel that uses the HTTP protocol. TcpChannel: Implements a channel that uses the TCP protocol (Transmission Control Protocol). Channel take stream of data and creates package for a transport protocol and sends to other machine. A simple architecture of .NET remoting is as in Fig 1.

As Fig.1 shows, Remoting system creates a proxy for the server object and a reference to the proxy will be returned to the client. When client calls a method, Remoting system sends request thro the channel to the server. Then client receives the response sent by the server process thro the proxy.
 
Example
Let us see a simple example which demonstrates .Net Remoting. In This example the Remoting object will send us the maximum of the two integer numbers sent.
Creating Remote Server and the Service classes on Machine 1: Please note for Remoting support your service (Remote object) should be derived from MarshalByRefObject.
    using System;  
    using System.Runtime.Remoting.Channels; //To support and handle Channel and channel sinks  
    using System.Runtime.Remoting;  
    using System.Runtime.Remoting.Channels.Http; //For HTTP channel  
    using System.IO;  
    namespace ServerApp {  
      public class RemotingServer {  
        public RemotingServer() {  
          //  
          // TODO: Add constructor logic here  
          //  
        }  
      }  
      //Service class  
      public class Service: MarshalByRefObject {  
        public void WriteMessage(int num1, int num2) {  
          Console.WriteLine(Math.Max(num1, num2));  
        }  
      }  
      //Server Class  
      public class Server {  
        public static void Main() {  
          HttpChannel channel = new HttpChannel(8001); //Create a new channel  
          ChannelServices.RegisterChannel(channel); //Register channel  
          RemotingConfiguration.RegisterWellKnownServiceType(typeof Service), "Service", WellKnownObjectMode.Singleton);  
        Console.WriteLine("Server ON at port number:8001");  
        Console.WriteLine("Please press enter to stop the server.");  
        Console.ReadLine();  
      }  
    }  
    }

Save the above file as ServerApp.cs. Create an executable by using Visual Studio.Net command prompt by, csc /r:system.runtime.remoting.dll /r:system.dll ServerApp.cs
 
A ServerApp.Exe will be generated in the Class folder.
 
Run the ServerApp.Exe will give below message on the console
 
Server ON at port number:8001
 
Please press enter to stop the server.
 
In order to check whether the HTTP channel is binded to the port, type http://localhost:8001/Service?WSDL in the browser. You should see a XML file describing the Service class.
 
Please note before running above URL on the browser your server (ServerApp.Exe should be running) should be ON.
 
Creating Proxy and the Client application on Machine 2
 
SoapSuds.exe is a utility which can be used for creating a proxy dll.
 
Type below command on Visual studio.Net command prompt.
 
soapsuds -url:http://< Machine Name where service is running>:8001/Service?WSDL -oa:Server.dll
 
This will generates a proxy dll by name Server.dll. This will be used to access remote object.
 
Client Code
    using System;  
    using System.Runtime.Remoting.Channels; //To support and handle Channel and channel sinks  
    using System.Runtime.Remoting;  
    using System.Runtime.Remoting.Channels.Http; //For HTTP channel  
    using System.IO;  
    using ServerApp;  
    namespace RemotingApp {  
      public class ClientApp {  
        public ClientApp() {}  
        public static void Main(string[] args) {  
          HttpChannel channel = new HttpChannel(8002); //Create a new channel  
          ChannelServices.RegisterChannel(channel); //Register the channel  
          //Create Service class object  
          Service svc = (Service) Activator.GetObject(typeof(Service), "http://<Machine name where Service running>:8001/Service"); //Localhost can be replaced by  
          //Pass Message  
          svc.WriteMessage(10, 20);  
        }  
      }  
    }

Save the above file as ClientApp.cs. Create an executable by using Visual Studio.Net command prompt by, csc /r:system.runtime.remoting.dll /r:system.dll ClientrApp.cs
 
A ClientApp.Exe will be generated in the Class folder. Run ClientApp.Exe , we can see the result on Running ServerApp.EXE command prompt.
 
In the same way we can implement it for TCP channel also.

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.NET 5 is the next version of .NET Core and the future of the .NET platform. With .NET 5 you have everything you need to build rich, interactive front end web UI and powerful backend services. .NET 5 contains great performance improvements in the runtime and libraries and for the gRPC components. These improvements, when applied to ASP.NET Core, result in some significant wins in throughput (RPS) and latency.

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This tutorial shows how to fix method not allowed on PUT and DELETE requests in ASP.NET Core.

After pushing code to the beta server, most of it was working fine. The front-end was being able to call GET, POST and OPTIONS requests normally. When trying to DELETE or PUT entries, however, the following error would show up on the browser’s console: 

 
Method not allowed? CORS error? What?

Initially, I was misled by the CORS error. Having had problems with this in the past, I thoroughly checked my API code for any possible problem in the configuration that could lead to this error only after deployed. I found none.

Then, it dawned on me that the CORS error could be not because my API wasn’t sending the ‘Access-Control-Allow-Origin’ on its response, but because it wasn’t being sent on the HTTP 405 error seen above.

Solution

What happens is that, when published, .NET Core enables the　WebDAVModule, which　disables PUT and DELETE requests　by default.

So, to solve the issue, I ended up disabling WebDAV in the whole application, by adding these lines to the auto-generated web.config:

<system.webServer>
  <modules runAllManagedModulesForAllRequests="false">
   <remove name="WebDAVModule" />
  /modules>
</system.webServer>

After restarting the API in IIS, TA-DA! Everything (or at least your PUT and DELETE requests) should be working normally.

I hope this will be helpful to someone that host ASP.NET website on Windows Server.

Today, in this article we will discuss the exception handling concept in any ASP.NET Core application. Exception handling is one of the most import functionality or part for any type of application which always need to be taken care and implement properly. Exceptions are mainly means for the run time errors which occur during the execution time of the application. So, if this type of error is not properly handled, then the application will be terminated.

In ASP.NET Core, the concept of exception handling has been changed, and rather to say, now it is in very much in better shape to implement exception handling. For any API projects implementing exception handling against every action, the method is quite time-consuming and it also requires extra efforts. So, for this purpose, we can implement the Global Exception handler so that all types of unhandled exceptions can be caught in this handler. The benefit of implementing a global exception handler is that we need to define this in one place. Through this handler, any exception that occurs in our application will be handled, even we ann new methods or controllers. So, in this article, we will discuss how to implement global exception handling in the ASP.NET Core Web API.

Create ASP.NET Core Web API Projects in Visual Studio 2019
So, before going to discuss the global exception handler, first, we need to create an ASP.NET Web API project. For this purpose, follow the steps mentioned below,

Now open the Microsoft Visual Studio and Click on Create a New Project
In the Create New Project dialog box, select ASP.NET Core Web Application for C# and then click on the Next Button.

In the Configure your new project window, provide the project name and then click on the Create button.
In the Create a New ASP.NET Core Web Application dialog, select API, and then click on Create Button.
Ensure that the checkboxes “Enable Docker Support” and “Configure for HTTPS” are unchecked. We won’t be using these features.
Ensure that “No Authentication” is selected as we won’t be using authentication either.
Click OK

Use the UseExceptionHandler middleware in ASP.NET Core
So, to implement the global exception handler, we can use the benefits of the ASP.NET Core build-in Middleware. A middleware is indicated as a software component inserted into the request processing pipeline which handles the requests and responses. We can use the ASP.NET Core in-build middleware UseExceptionHandler to use as a global exception handler. The ASP.NET Core request processing pipeline includes a chain of middleware components. This pipeline in turn contains a series of request delegates that are invoked one after another. While the incoming requests flow through each of the middleware components in the pipeline, each of these components can either process the request or pass the request to the next component in the pipeline.

Through this middleware, we can get all the detailed information of the exception object like the Stack trace, inner exception, message, etc., and also return that information through the API to return as an output. We need to put the exception handler middleware inside the configure() of a startup.cs file. If we use any MVC based application, then we can use the exception handler middleware just as below. This code snippet demonstrates how we can configure the UseExceptionHandler middleware to redirect the user to an error page when any type of exception has occurred.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)  
{  
app.UseExceptionHandler("/Home/Error");  
app.UseMvc();  
}  

Now, we need to check this exception message. For that purpose, open the WeatherForecastController.cs file and add the below action method to throw an exception –
[Route("GetExceptionInfo")]  
[HttpGet]  
public IEnumerable<string> GetExceptionInfo()  
{  
string[] arrRetValues = null;  
if (arrRetValues.Length > 0)  
{ }  
return arrRetValues;  
}  

If we want to capture the details of the exception objects – i.e. like the stack trace, message, etc then we use the below code as the exception middleware –
app.UseExceptionHandler(  
    options =>  
    {  
        options.Run(  
            async context =>  
            {  
                context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;  
                context.Response.ContentType = "text/html";  
                var exceptionObject = context.Features.Get<IExceptionHandlerFeature>();  
                if (null != exceptionObject)  
                {  
                    var errorMessage = $"<b>Exception Error: {exceptionObject.Error.Message} </b> {exceptionObject.Error.StackTrace}";  
                    await context.Response.WriteAsync(errorMessage).ConfigureAwait(false);  
                }  
            });  
    }  
);  

For checking the output, just execute the API endpoint in any browser:

Define a Custom Exception Middleware to handle Exceptions in ASP.NET Core API
Also, we can write our custom middleware to handle any type of exceptions. In this section, we demonstrate how to create a typical custom middleware class. Custom middleware also provides much more flexibility to handle exceptions. We can add a stack trace, an exception type name, error code, or anything else which we want to include as a part of the error message. The below code snippet shows the typical custom middleware class:
    using Microsoft.AspNetCore.Http;    
    using Newtonsoft.Json;    
    using System;    
    using System.Collections.Generic;    
    using System.Linq;    
    using System.Net;    
    using System.Threading.Tasks;    
        
    namespace API.DemoSample.Exceptions    
    {    
        public class ExceptionHandlerMiddleware    
        {    
            private readonly RequestDelegate _next;    
        
            public ExceptionHandlerMiddleware(RequestDelegate next)    
            {    
                _next = next;    
            }    
        
            public async Task Invoke(HttpContext context)    
            {    
                try    
                {    
                    await _next.Invoke(context);    
                }    
                catch (Exception ex)    
                {    
                        
                }    
            }    
        }    
    }    

In the above class, a request delegate is passed to any middleware. The middleware either processes this or passes it to the next middleware in the chain. If the request is unsuccessful, then an exception will be thrown, and then the HandleExceptionMessageAsync method will be executed within the catch block. So, let's update the Invoke method code as shown below:
    public async Task Invoke(HttpContext context)  
            {  
                try  
                {  
                    await _next.Invoke(context);  
                }  
                catch (Exception ex)  
                {  
                    await HandleExceptionMessageAsync(context, ex).ConfigureAwait(false);  
                }  
            }  

Now, we need to implement the HandleExceptionMessageAsync method, as shown below:
    private static Task HandleExceptionMessageAsync(HttpContext context, Exception exception)  
            {  
                context.Response.ContentType = "application/json";  
                int statusCode = (int)HttpStatusCode.InternalServerError;  
                var result = JsonConvert.SerializeObject(new  
                {  
                    StatusCode = statusCode,  
                    ErrorMessage = exception.Message  
                });  
                context.Response.ContentType = "application/json";  
                context.Response.StatusCode = statusCode;  
                return context.Response.WriteAsync(result);  
            }  

Now, in the next step, we need to create a static class named ExceptionHandlerMiddlewareExtensions and add the below code within that class,
    using Microsoft.AspNetCore.Builder;  
    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Threading.Tasks;  
      
    namespace API.DemoSample.Exceptions  
    {  
        public static class ExceptionHandlerMiddlewareExtensions  
        {  
            public static void UseExceptionHandlerMiddleware(this IApplicationBuilder app)  
            {  
                app.UseMiddleware<ExceptionHandlerMiddleware>();  
            }  
        }  
    }  

Now, in the last step, we need to turn on our custom middleware within the Configure method of the startup class, as shown below:
    app.UseExceptionHandlerMiddleware();  

Conclusion
Exception handling is a mainly cross-cutting concept for any type of application. In this article, we discuss the implementation process of the global exception handling concept. We can take the benefits of global exception handling in any ASP.NET Core application to ensure that every exception will be caught and return the proper details related to that exception. With the global exception handling, we just need to write the exception handling related code for our entire application just in one place. Any suggestions or feedback or query related to this article are most welcome.

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High-level goals for .NET 5 include providing a unified .NET SDK experience, with a single BCL (base class library) across all .NET 5 applications, and with support for both native and web applications across multiple operating systems. A single .NET 5 native application project would support targets such as Windows, Microsoft Duo (Android), and Apple iOS using native controls on those platforms.

Additional goals of .NET 5 include support for building high-performance cloud applications, faster algorithms in the BCL, better support for containers in the runtime, and support for HTTP3.　.NET 5.0 includes support for the WebAssembly binary format, via the Mono runtime and .NET libraries. A set of nullable reference type annotations also is featured.

As we know that ASP.NET 5 can work with two different environment　.NET core　and .NET Framework to provide you a better experience and flexibility.

The .NET core runtime is a cross-platform and modular runtime with a small impression. .NET Core runtime has the following benefits.

• You can run your application with a deployed version of runtime instead of that runtime which is installed on a host operating system. That makes easy to the app deployment and framework update.
• The ASP.NET 5 provides a cross-platform version of .NET Core for Linux, Mac, and Windows operating system rather than that operating system you use for development.
• .NET Core runtime will never ask you for update the runtime feature which is not relevant to your application. You can save your time on testing and deploying updates.

2. Fast HTTP performance

ASP.NET 5 has introduced a modular HTTP request pipeline so you can add the component according to your requirements. A pipeline does not depend on system.web. By reducing upward in pipeline app can work better and tuned better HTTP stack. The pipeline is also supported OWIN.

You can use the configure method in your Startup class to customize the pipeline the configure method used to specify which middleware you want to use in your requested pipeline. ASP.NET 5 has introduced many different middlewares from katana project including middleware for authentication, diagnostics, and static files.

3. Dependency injection

ASP.NET Frameworks like SignalR, Web API and MVC supports the dependency injection but not the holistic way and consistent through the entire web stack. You can access service in middleware, in filters,　 at startup, in model binding, virtually any part of the pipeline and in controllers wherever you want use your service. ASP.NET 5 has a minimum dependency injection container to bootstrap the system. but it also provides the facility of changing containers of your choice like Ninject, Autofac, etc.

4. Cloud-ready configure

The best feature of ASP.NET 5 is you not need to use Web.config file for configuration. The main aim of ASP.NET 5 is making easy to deploy an application to the cloud and automatically read the correct configuration value for particular environment. The new system allows you to request name value from different sources like XML, environment variable and XML you have to decide which format is best in your scenario.

5. MVC 6 – a unified programming model

Web API, Web Pages, and MVC frequently used together in developing solution and they provide complementary functionality. in past ASP.NET release, this framework was implemented separately due to this they have inconsistencies and duplication issues. In MVC 6 we can merge those models in a single programming model. Now you are able to create a single web app that handles the data services and Web UI without reconciling in the programing framework. You also able to transition a site first developed with a web page into a more robust MVC app.

Now you can return content-negotiated data and Razor views from same controller and using same MVC filter pipeline.

Conclusion

The .NET 5 project is an important and exciting new direction for .NET. You will see .NET become simpler but also have broader and more expansive capability and utility. All new development and feature capabilities will be part of .NET 5, including new C# versions.

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