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European ASP.NET Core Hosting :: ASP.NET Core 2.0 MVC Filters

clock January 28, 2019 09:58 by author Scott

The following is tutorial how to run code before and after MVC request pipeline in ASP.NET Core.

Solution

In an empty project update Startup class to add services and middleware for MVC:

        public void ConfigureServices
            (IServiceCollection services)
        {
            services.AddMvc();
        } 

        public void Configure(
            IApplicationBuilder app,
            IHostingEnvironment env)
        {
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });
        }

Add the class to implement filter:

    public class ParseParameterActionFilter : Attribute, IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            object param;
            if (context.ActionArguments.TryGetValue("param", out param))
                context.ActionArguments["param"] = param.ToString().ToUpper();
            else
                context.ActionArguments.Add("param", "I come from action filter");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        {
        }
    }

In the Home controller add an action method that uses Action filter:

        [ParseParameterActionFilter]
        public IActionResult ParseParameter(string param)
        {
            return Content($"Hello ParseParameter. Parameter: {param}");
        }

Browse to /Home/ParseParameter, you’ll see:

 

Discussion

Filter runs after an action method has been selected to execute. MVC provides built-in filters for things like authorisation and caching. Custom filters are very useful to encapsulate reusable code that you want to run before or after action methods.

Filters can short-circuit the result i.e. stops the code in your action from running and return a result to the client. They can also have services injected into them via service container, which makes them very flexible.

Filter Interfaces

Creating a custom filter requires implementing an interface for the type of filter you require. There are two flavours of interfaces for most filter type, synchronous and asynchronous:

    public class HelloActionFilter : IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            // runs before action method
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        {
            // runs after action method
        }
    } 

    public class HelloAsyncActionFilter : IAsyncActionFilter
    {
        public async Task OnActionExecutionAsync(
            ActionExecutingContext context,
            ActionExecutionDelegate next)
        {
            // runs before action method
            await next();
            // runs after action method
        }
    }

You can short-circuit the filter pipeline by setting the Result (of type IActionResult) property on context parameter (for Async filters don’t call the next delegate):

    public class SkipActionFilter : Attribute, IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.Result = new ContentResult
            {
                Content = "I'll skip the action execution"
            };
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    } 

    [SkipActionFilter]
    public IActionResult SkipAction()
    {
       return Content("Hello SkipAction");
    }

For Result filters you could short-circuit by setting the Cancel property on context parameter and sending a response:

        public void OnResultExecuting(ResultExecutingContext context)
        {
            context.Cancel = true;
            context.HttpContext.Response.WriteAsync("I'll skip the result execution");
        } 

        [SkipResultFilter]
        public IActionResult SkipResult()
        {
            return Content("Hello SkipResult");
        }

Filter Attributes

MVC provides abstract base classes that you can inherit from to create custom filters. These abstract classes inherit from Attribute class and therefore can be used to decorate controllers and action methods:

  • ActionFilterAttribute
  • ResultFilterAttribute
  • ExceptionFilterAttribute
  • ServiceFilterAttribute
  • TypeFilterAttribute

Filter Types

There are various type of filters that run at different stages of the filter pipeline. Below a figure from official documentation illustrates the sequence:

 

 

Authorization

 

 

This is the first filter to run and short circuits request for unauthorised users. They only have one method (unlike most other filters that have Executing and Executed methods). Normally you won’t write your own Authorization filters, the built-in filter calls into framework’s authorisation mechanism.

Resource

They run before model binding and can be used for changing how it behaves. Also they run after the result has been generated and can be used for caching etc.

Action

They run before and after the action method, thus are useful to manipulate action parameters or its result. The context supplied to these filters let you manipulate the action parameters, controller and result.

Exception

They can be used for unhandled exception before they’re written to the response. Exception handling middleware works for most scenarios however this filter can be used if you want to handle errors differently based on the invoked action.

Result

They run before and after the execution of action method’s result, if the result was successful. They can be used to manipulate the formatting of result.

Filter Scope

Filters can be added at different levels of scope: Action, Controller and Global. Attributes are used for action and controller level scope. For globally scoped filters you need to add them to filter collection of MvcOptions when configuring services in Startup:

            services.AddMvc(options =>
            {
                             // by instance
                options.Filters.Add(new AddDeveloperResultFilter("Tahir Naushad")); 

                // by type
                options.Filters.Add(typeof(GreetDeveloperResultFilter));
            });

Filters are executed in a sequence:

1. The Executing methods are called first for Global > Controller > Action filters.

2. Then Executed methods are called for Action > Controller > Global filters.

Filter Dependency Injection

In order to use filters that require dependencies injected at runtime, you need to add them by Type. You can add them globally (as illustrated above), however, if you want to apply them to action or controller (as attributes) then you have two options:

ServiceFilterAttribute

This attributes retrieves the filter using service container. To use it:

Create a filter that uses dependency injection:

    public class GreetingServiceFilter : IActionFilter
    {
        private readonly IGreetingService greetingService; 

        public GreetingServiceFilter(IGreetingService greetingService)
        {
            this.greetingService = greetingService;
        } 
        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.ActionArguments["param"] =
                this.greetingService.Greet("James Bond");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    }

Add filter to service container:

services.AddScoped<GreetingServiceFilter>();

Apply it using ServiceFilterAttribute:

[ServiceFilter(typeof(GreetingServiceFilter))]
public IActionResult GreetService(string param)

TypeFilterAttribute

This attributes doesn’t need registering the filter in service container and initiates the type using ObjectFactory delegate. To use it:

Create a filter that uses dependency injection:

    public class GreetingTypeFilter : IActionFilter
    {
        private readonly IGreetingService greetingService; 

        public GreetingTypeFilter(IGreetingService greetingService)
        {
            this.greetingService = greetingService;
        } 

        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.ActionArguments["param"] = this.greetingService.Greet("Dr. No");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    }

Apply it using TypeFilterAttribute:

[TypeFilter(typeof(GreetingTypeFilter))]
public IActionResult GreetType1(string param)

You could also inherit from TypeFilterAttribute and then use without TypeFilter:

public class GreetingTypeFilterWrapper : TypeFilterAttribute
{
   public GreetingTypeFilterWrapper() : base(typeof(GreetingTypeFilter))
   { }


[GreetingTypeFilterWrapper]
public IActionResult GreetType2(string param)
 



European ASP.NET Hosting :: How to Add Custom 404 and Error Pages in ASP.NET

clock January 23, 2019 10:26 by author Scott

I post this to remind myself how we got this working for both ASP.NET and static files, both for remote and local requests on IIS 7 and IIS 7.5.

<httpErrors> over <customErrors>

<customErrors> in web.config is a construct for specifying custom error pages for requests handled by ASP.NET. In other words, static files such as HTML files or directory (“friendly”) URLs are not handled.

<httpErrors> configures error pages in IIS itself, outside the web application. This handles all requests, whether they’re in fact handled by ASP.NET or IIS natively.

We ignore customErrors altogether and only use httpErrors.

Displaying a static HTML file

This is useful for error codes such as 500 where the ASP.NET web application in itself may suffer problems:

<httpErrors errorMode="Custom" defaultResponseMode="File">
    <clear />
    <error statusCode="500" path="Static\html\error.html"/>
</httpErrors>

Displaying an ASP.NET page

This displays an ASP.NET page when a 404 error occurs, without rewriting the URL (the visitor will still see the requested URL in the address bar):

<httpErrors errorMode="Custom" existingResponse="Replace">
  <remove statusCode="404" subStatusCode="-1" />
  <error statusCode="404" path="/Errors/404.aspx" responseMode="ExecuteURL"/>
</httpErrors>

Note that we skip the <clear /> element and simply remove the standard 404 handling (in order to avoid an exception caused by duplicate elements for the 404 status code).

Redirecting to another URL

ExecuteURL can only be used to execute an ASP.NET file within the same application. If we want to redirect to another application, or possibly an entirely different external URL, we use the Rewrite response mode with an absolute URL:

<httpErrors errorMode="Custom" existingResponse="Replace">
  <clear />
  <error statusCode="404" path="http://www.bing.com" responseMode="Redirect"/>
</httpErrors>

Make sure HTTP errors is enabled in IIS

For this to work you have to make sure the HTTP Errors feature is installed for IIS, otherwise you’ll just get an empty 404 response:



ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: What Is SSL Or TLS?

clock January 15, 2019 10:10 by author Peter

Many people are using these terms interchangeably. But the correct term is TLS. Well, let us understand what this TLS is and why we really need it.
 
Most of us are already aware that HTTP is a plain text protocol which doesn’t have its own transport security mechanisms. In other words, HTTP is a protocol which sends the data to a server and gets a response without any built-in feature or mechanism to protect the data packet against tampering.
 
To protect our packet which is traveling through HTTP, some sort of secure tunneling is required and that secure tunneling is provided by a protocol called TLS, a.k.a., SSL. Here, HTTP and TLS come together.
 
Usually, people associate SSL/TLS with encryption, but that is not the only feature SSL provides. There are a few more features, such as -
  • Server Authentication – It makes sure that the communication with the right server is made.
  • Veracity Protection – It promotes integrity and makes sure that no one in between is reading our data.
  • Confidentiality – It makes sure that no one should know what data is being transmitted.
Associating the above features with HTTP makes HTTPS more reliable and authentic. Now, the question arises --  how to achieve this or how to implement this SSL. Wait for my next blog to learn more about SSL certificates.

HostForLIFE.eu ASP.NET Core 2.2.1 Hosting
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ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: How To Serialize Nonstandard Enum Values?

clock January 7, 2019 11:35 by author Peter

Introduction
.NET client libraries that integrate with third-party APIs occasionally need to compromise on how enum values are represented in model classes. For example, an API that requires values to be expressed in all uppercase letters force the creation of an enum similar to:

public enum YesNoMaybeEnum  
 {  
     YES,  
     NO,  
     MAYBE   
 }  


While this will compile, it violates .NET naming conventions. In other cases, the third party may include names that include invalid characters like dashes or periods. For example, Amazon's Alexa messages include a list of potential request types that include a period in the names. These values cannot be expressed as enumation names. While this could be addressed by changing the data type of the serialized property from an enumeration to a string, the property values are no longer constrained and any suggestions from Intellisense are lost.

This article demonstrates how to eat your cake and have it, too. Using attributes and reflection, values can be serialized to and deserialized from JSON.

Serialization with EnumDescription
Let's say we need to serialize values that include periods. Creating an enum like the following generates compile time errors,

public enum RequestTypeEnum  
{  
    LaunchRequest,  
    IntentRequest,  
    SessionEndedRequest,  
    CanFulfillIntentRequest,  
    AlexaSkillEvent.SkillPermissionAccepted,  
    AlexaSkillEvent.SkillAccountLinked,  
    AlexaSkillEvent.SkillEnabled,  
    AlexaSkillEvent.SkillDisabled,  
    AlexaSkillEvent.SkillPermissionChanged,  
    Messaging.MessageReceived  
}  

The EnumMember attribute defines the value to serialize when dealing with data contracts. Samples on Stack Overflow that show enumeration serialization tend to use the Description attribute. Either attribute can be used or you can create your own. The EnumMember attribute is more tightly bound to data contract serialization while the Description attribute is for use with design time and runtime environments, the serialization approach in this article opts for the EnumMember. After applying the EnumMember and Data Contract attributes, the enum now looks like,

[DataContract(Name = "RequestType")]    
public enum RequestTypeEnum    
{    
    [EnumMember(Value = "LaunchRequest")]    
    LaunchRequest,    
    [EnumMember(Value = "IntentRequest")]    
    IntentRequest,    
    [EnumMember(Value = "SessionEndedRequest")]    
    SessionEndedRequest,    
    [EnumMember(Value = "CanFulfillIntentRequest")]    
    CanFulfillIntentRequest,    
    [EnumMember(Value = "AlexaSkillEvent.SkillPermissionAccepted")]    
    SkillPermissionAccepted,    
    [EnumMember(Value = "AlexaSkillEvent.SkillAccountLinked")]    
    SkillAccountLinked,    
    [EnumMember(Value = "AlexaSkillEvent.SkillEnabled")]    
    SkillEnabled,    
    [EnumMember(Value = "AlexaSkillEvent.SkillDisabled")]    
    SkillDisabled,    
    [EnumMember(Value = "AlexaSkillEvent.SkillPermissionChanged")]    
    SkillPermissionChanged,    
    [EnumMember(Value = "Messaging.MessageReceived")]    
    MessageReceived    
}    

The EnumMember attribute is also applied to enum members without periods. Otherwise, the DataContractSerilizer would serializes the numeric representation of the enumeration value. Now we can define a DataContract with,
[DataContract]  
public class SamplePoco  
{  
    [DataMember]  
    public RequestTypeEnum RequestType { get; set; }  
}
 

And serialize it to XML with,
SamplePoco enumPoco = new SamplePoco();  
enumPoco.RequestType = RequestTypeEnum.SkillDisabled;  
DataContractSerializer serializer = new DataContractSerializer(typeof(SamplePoco));  
 
var output = new StringBuilder();  
using (var xmlWriter = XmlWriter.Create(output))  
{  
    serializer.WriteObject(xmlWriter, enumPoco);  
    xmlWriter.Close();  
}  
string xmlOut = output.ToString();   


This generates the following XML,
<?xml version="1.0" encoding="utf-16"?><SamplePoco xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/EnumSerializationSample"><RequestType>AlexaSkillEvent.SkillDisabled</RequestType>  
</SamplePoco>  


DataContract serialization is sorted out, but doesn't yet address JSON serialization.

JSON Serialization

If you need to work with any REST API endpoints, then you'll need to support JSON. The NewtonSoft JSON has its own serialization strategy, and so the EnumMember attribute needs to be leveraged to integrate with it using a custom JsonConverter, but before taking that step, the enumation value must be read from the attribute.

This method accepts an enum value and returns the string value in the EnumMember attribute.
private string GetDescriptionFromEnumValue(Enum value)  
        {  
 
#if NETSTANDARD2_0  
            EnumMemberAttribute attribute = value.GetType()  
                .GetField(value.ToString())  
                .GetCustomAttributes(typeof(EnumMemberAttribute), false)  
                .SingleOrDefault() as EnumMemberAttribute;  
 
            return attribute == null ? value.ToString() : attribute.Value;  
#endif  
 
#if NETSTANDARD1_6 || NETSTANDARD1_3 || NET45 || NET47  
 
            EnumMemberAttribute attribute = value.GetType()  
                .GetRuntimeField(value.ToString())  
                .GetCustomAttributes(typeof(EnumMemberAttribute), false)  
                .SingleOrDefault() as EnumMemberAttribute;  
 
            return attribute == null ? value.ToString() : attribute.Value;  
            
#endif  
              throw new NotImplementedException("Unsupported version of .NET in use");  
        }  


There's a subtle difference between the .NET Standard 2.0 implementation and the others. In .NET Standard 1.6 and prior versions, use the GetRuntimeField method to get a property from a type. In .NET Standard 2.0, use the GetField method to return the property of a type. The compile-time constants and checks in the GetDescriptionFromEnumValue abstract away that complexity.  

Coming the other way, a method needs to take a string and convert it to the associated enumeration.
public T GetEnumValue(string enumMemberText)   
{  
 
    T retVal = default(T);  
 
    if (Enum.TryParse<T>(enumMemberText, out retVal))  
        return retVal;  
 
      var enumVals = Enum.GetValues(typeof(T)).Cast<T>();  
 
    Dictionary<string, T> enumMemberNameMappings = new Dictionary<string, T>();  
 
    foreach (T enumVal in enumVals)  
    {  
        string enumMember = enumVal.GetDescriptionFromEnumValue();  
        enumMemberNameMappings.Add(enumMember, enumVal);  
    }  
 
    if (enumMemberNameMappings.ContainsKey(enumMemberText))  
    {  
        retVal = enumMemberNameMappings[enumMemberText];  
    }  
    else  
        throw new SerializationException($"Could not resolve value {enumMemberText} in enum {typeof(T).FullName}");  
 
    return retVal;  
}  

The values expressed in the EnumMember attributes are loaded into a dictionary. The value of the attribute serves as the key and the associated enum is the value. The dictionary keys are compared to the string value passed to the parameter and if a matching EnumMember value is found, then the related enum is returned and so "AlexaSkillEvent.Enabled" returns RequestTypeEnum.SkillEnabled.
Using this method in a JSON Converter, the WriteJson method looks like the following,
public class JsonEnumConverter<T> : JsonConverter where T : struct, Enum, IComparable, IConvertible, IFormattable
{  
 
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)  
    {  
        if (value != null)  
        {  
            Enum sourceEnum = value as Enum;  
 
            if (sourceEnum != null)    
            {  

                string enumText = GetDescriptionFromEnumValue(sourceEnum);  
                writer.WriteValue(enumText);  
            }  
        }  
    }  


Please note that an enum constraint is applied to the generic type class declaration. This wasn't possible until C# version 7.3. If you cannot upgrade to use C# version 7.3, just remove this constraint.

The corresponding ReadJson method is,
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)  
{  
      object val = reader.Value;  
      if (val != null)  
    {  
        var enumString = (string)reader.Value;  
          return GetEnumValue(enumString);  
    }  
      return null;  
}  


Now the class definition needs to apply the JsonConverter class to the RequestType property,
[DataContract]  
public class SamplePoco  
{  
    [DataMember]  
    [JsonConverter(typeof(JsonEnumConverter<RequestTypeEnum>))]  
    public RequestTypeEnum RequestType { get; set; }  
 
 

Finally, the SamplePoco class is serialized to JSON,
SamplePoco enumPoco = new SamplePoco();  
enumPoco.RequestType = RequestTypeEnum.SkillEnabled;  
string samplePocoText = JsonConvert.SerializeObject(enumPoco);  
This generates the following JSON,
{  
"RequestType":"AlexaSkillEvent.SkillEnabled"  
}  

And deserialing the JSON yields the RequestTypeEnum.SkillEnabled value on the sample class.

string jsonText = "{\"RequestType\":\"AlexaSkillEvent.SkillEnabled\"}";  
SamplePoco sample = JsonConvert.DeserializeObject<SamplePoco>(jsonText); 

HostForLIFE.eu ASP.NET Core 2.2.1 Hosting
European best, cheap and reliable ASP.NET hosting with instant activation. HostForLIFE.eu is #1 Recommended Windows and ASP.NET hosting in European Continent. With 99.99% Uptime Guaranteed of Relibility, Stability and Performace. HostForLIFE.eu security team is constantly monitoring the entire network for unusual behaviour. We deliver hosting solution including Shared hosting, Cloud hosting, Reseller hosting, Dedicated Servers, and IT as Service for companies of all size.



ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: Handling Multiple Instances Of Caching Providers Using EasyCaching

clock December 18, 2018 10:09 by author Peter

Most of the time, we may use one type of caching in our projects, such as Redis or InMemory etc. However, we may often need two or three types of caching depending on the requirement of our project. In this article, I will show you how to solve this problem of multiple caching needs by using EasyCahing with ASP.NET Core. For more information about EasyCaching, you can follow my past articles about it or visit its GitHub page. Now, let's begin.

Solution
We are using IEasyCachingProviderFactory to get the caching providers that you want to use. We shall install the latest version (this time, it is v0.4.0) of EasyCaching here because it incorporates the new features of EasyCaching. Add InMemory and Redis - the two providers into your project.
    dotnet add package EasyCaching.Redis --version 0.4.0 
    dotnet add package EasyCaching.InMemory --version 0.4.0 


Before we use it, we need to configure it in the Startup class. Here, we will use two types of caching providers with three instances - one in-memory caching provider and two Redis caching providers.
    public void ConfigureServices(IServiceCollection services) 
    { 
        //other ..     
        //configure the in-memory caching provider 
        services.AddDefaultInMemoryCacheWithFactory("inmemory"); 
     
        //configure the first redis caching provider 
        services.AddDefaultRedisCacheWithFactory("redis1",option => 
        { 
            option.DBConfig.Endpoints.Add(new ServerEndPoint("127.0.0.1", 6379)); 
        }); 
     
        //configure the second redis caching provider 
        services.AddDefaultRedisCacheWithFactory("redis2", option => 
        { 
            option.DBConfig.Endpoints.Add(new ServerEndPoint("127.0.0.1", 6380)); 
        }); 
    } 


Note
Here, we used AddDefaultInMemoryCacheWithFactory and AddDefaultRedisCacheWithFactory to replace the AddDefaultInMemoryCache and AddDefaultRedisCache respectively.This is an important step to deal with factory.
 
After configuring the factory, we can use it via dependency injection where we need to use. For example, the following code shows how to use IEasyCachingProviderFactory in the controller.
    [Route("api/[controller]")] 
    public class ValuesController : Controller 
    { 
        private readonly IEasyCachingProviderFactory _factory; 
     
        public ValuesController(IEasyCachingProviderFactory factory) 
        { 
            this._factory = factory; 
        } 
     
        // GET api/values/inmem 
        [HttpGet] 
        [Route("inmem")] 
        public string GetInMemory() 
        { 
            var provider = _factory.GetCachingProvider("inmemory"); 
            var val = $"memory-{Guid.NewGuid()}"; 
            var res = provider.Get("named-provider", () => val, TimeSpan.FromMinutes(1)); 
            Console.WriteLine($"Type=InMemory,Key=named-provider,Value={res},Time:{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}"); 
            return $"cached value : {res}";                
        } 
     
        // GET api/values/redis1 
        [HttpGet] 
        [Route("redis1")] 
        public string GetRedis1() 
        { 
            var provider = _factory.GetCachingProvider("redis1"); 
            var val =  $"redis1-{Guid.NewGuid()}"; 
            var res = provider.Get("named-provider", () => val, TimeSpan.FromMinutes(1)); 
            Console.WriteLine($"Type=redis1,Key=named-provider,Value={res},Time:{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}"); 
            return $"cached value : {res}"; 
        } 
         
        // GET api/values/redis2 
        [HttpGet] 
        [Route("redis2")] 
        public string GetRedis2() 
        { 
            var provider = _factory.GetCachingProvider("redis2"); 
            var val =  $"redis2-{Guid.NewGuid()}"; 
            var res = provider.Get("named-provider", () => val, TimeSpan.FromMinutes(1)); 
            Console.WriteLine($"Type=redis2,Key=named-provider,Value={res},Time:{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}"); 
            return $"cached value : {res}"; 
        } 
    } 

GetCachingProvider is the key method to get the registered caching providers via their name. This name must be the same as what we registered in the configuration. If we pass a not registered or not existed caching provider name to this method, it will throw an exception with a message to tell us that it can not find a matching caching provider!
 
Now, let's take a look at the result when we visit those three APIs.

Using EasyCaching To Handle Multiple Instance Of Caching Providers. We visited http://localhost:9999/api/values/inmem, http://localhost:9999/api/values/redis1, and http://localhost:9999/api/values/redis2 one by one. The first time, all the cached values will be initialized.
The second time, all the cached values were the same as the first time because they're still valid. The third time, after the expiration, all the cached values were changed!
 
The result tells us that all the caching providers will not affect others. In this article, I showed you how to handle multiple instances of caching providers when using EasyCaching in your ASP.NET Core project! The way to get a caching provider is similar to creating a new instance of HttpClient via HttpClientFactory.

HostForLIFE.eu ASP.NET Core 2.2.1 Hosting
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ASP.NET Core 2.2 Hosting - HostForLIFE.eu :: How .NET Support Multiple Languages?

clock December 13, 2018 10:27 by author Peter

An application is said to be multilingual if it can be deployed in many different languages. With .NET, all of the languages including Visual Basic, .NET, C#, and J# compile to a common Intermediate language (IL). This makes all languages interoperable. Microsoft has created Java bytecode, which is a low-level language with a simple syntax, which can be very quickly translated into native machine code.

CLR
.NET Framework is a multilingual application because of CLR. CLR is the key of .NET Framework. The code running under the control of the CLR is often termed as managed code.

The main task of CLR is to convert compiled code into the native code.
.NET Framework has one or more compilers; for e.g., VB .NET, C#, C++, JScript or any third party compiler such as COBOL. Anyone of these compilers will convert your source code into Microsoft Intermediate Language (MSIL). The main reason for .NET to be multilingual is that you can compile your code from IL and this compiled code will be interoperable with the code that has been compiled to IL from another language.

It simply means that you can create pages in different languages (like C#, VB .NET, J# etc.) and once all of these pages are compiled they all can be used in a single application. Let us understand this point clearly with an example.

Let us consider a situation where a customer needs an application to be ready in 20 days. For completing the application in 20 days we want 30 developers who all know the specific language but we have 15 developers who know C# and 15 developers who know VB .NET. In this situation, if we don’t use .NET then we need to hire 15 more developers of C# or VB .NET which is a difficult and costly solution. Now, if we use .NET then we can use C# and VB .NET language in the same application. This is possible because once C# code is compiled from IL it becomes interoperable with VB .NET code which is compiled from IL.

Then JIT (Just In Time) of CLR converts this MSIL code into native code using metadata which is then executed by OS.

CLR stands for common language runtime. Common language runtime provides other services like memory management, thread management, remoting, and other security such as CTS and CLS.

CLR is a layer between an operating system and .NET language, which uses CTS and CLS to create code.

CTS
CTS stands for the common type system. CTS defines rules that common language runtime follows when we are declaring, using and managing type. CTS deals with the data type. .NET supports many languages and every language has its own data type. One language cannot understand data types of another language.

For example: When we are creating an application in C#, we have int and when we are creating an application in VB .NET, we have an integer. Here CTS comes into play --  after the compilation, CTS converts int and integer into the int32 structure.

CLS
CLS stands for common language specification.
CLS is a subset of CTS and it declares all the rules and restrictions that all languages under .NET Framework must follow. The language which follows these rules is known as CLS compliant.
For example, we can use multiple inheritances in c++ but when we use the same code in C# it creates a problem because C# does not support multiple inheritances. Therefore, CLS restricts multiple inheritances for all language.

One other rule is that you cannot have a member with the same name and a different case. In C# add() and Add() are different because it is case sensitive but a problem arises when we use this code in VB .NET because it is not case-sensitive and it considers add() and Add() as the same.

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ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: The Common Language Runtime Of Microsoft’s .Net Framework

clock December 5, 2018 10:02 by author Peter

The CLR is a runtime environment of .NET to execute applications. The major function of the CLR is converting the Managed Code to native code and executing the program. Furthermore, it acts as a layer between operating systems and apps that are written in .NET languages. The common language runtime handles execution of code as well as provides useful services for implementing the program. Aside from code execution, the CLR also provides services like memory management, security management, thread management, compilation, code verification, and other system services.

CLR is due for a makeover
The common language runtime of Microsoft is due for a makeover with Microsoft announcing plans to make it more scalable and efficient. The key to the modernization would be enhancements on the intermediate language underlying the CRL, called IL, that has not been upgraded in a decade. Microsoft wants to boost the IL as well as make the CLR a richer target for programming languages. The aim of the common language runtime is to run .NET programs in an efficient manner.

One imminent enhancement includes Span<T>, pronounced ‘span of tee’. It’s a new kind that would offer framework and language features to achieve more performing, safer, low-level code. The T in Span<T> means type parameter. It would be used by C# as well as other languages to build more efficient code, which does not require copying big amounts of data or pause for garbage collection. New CRL versions would have ‘inside knowledge’ regarding Span<T> to boost speed. It will be rolled out in the next few releases of .NET.

Serving as the counterpart of Microsoft to the JVM of the world of Java, the common language runtime provides management of code of .NET languages, which include Visual Basic, C# and F#. The source code is compiled by the language compilers to the IL code. The CLR tunes the program through the execution of the IL and translating output into a machine code while the program runs. Other services are provided by the common language runtime include automatic management of memory and type safety, saving .NET programmers from providing the services.

THE ROLE OF THE COMMON LANGUAGE RUNTIME IN THE DOT NET FRAMEWORK
  1. Base Class libraries
    Provides class libraries support to an app when required.
  2. Thread support
    Threads are managed under the CLR. Threading means the parallel execution of code. Basically, threads are lightweight processes that are responsible for multi-tasking in a single app.
  3. MSIL code to native code
    The CLR is an engine that compiles the source code to an intermediate language. The intermediate language’s called the Microsoft Intermediate Language. During program execution, the MSIL’s converted to the native code of the machine code. The conversion is possible via the Just-In-Time compiler. At compilation, the end result is the PE or the Portable Executable file.
  4. Code Manager
    The common language runtime manages code. When compiling a .NET app, one does not generate code that could actually execute on the machine. The MSIL or the Microsoft Intermediate Language or IL could actually be generated. All code of .NET is IL code. The IL code is also called the Managed Code since the CLR of.NET manages it.
  5. COM Marshaler
    It enables communication between the app and COM objects.
  6. CLS or Common Language Specification
    It is used to communicate objects that are written in various .NET languages. It defines the standards and rules to which languages should adhere to in order to be compatible with the other languages of .NET. This lets C# developers to inherit from classes, which are defined in VB.NET or other compatible languages of .NET.
  7. Debug Engine
    The CLR enables performing debugging an app during runtime.
  8. Type Checker
    It verifies the types used in the app with CLS or CTS standards that are supported by the common language runtime and provides type safety.
  9. CTS or the Common Type System
    It specifies types of data that are created in a couple of different languages compiled into the base common data type system.
  10. Security Engine
    This enforces security permission at code level security, machine level security and folder level security with the use of .NET framework setting and tools provided by .NET.
  11. Exception Manager
    It handles exceptions thrown by an app while executing Try-catch block that is provided by an exception. In ‘Try’ block used where a code part expects an error. In ‘Catch’ block throws exception caught from the ‘try’ block. If there’s no catch block, it would terminate an app.
  12. Garbage Collector
    The Garbage Collectors handles automatic memory management. Furthermore, it releases memory of unused objects in an app that provides automatic memory management.
Hire ASP.NET developers from India for maximum results and solutions. With the improvements set to boost the .NET’s CLR, applications, and solutions are more effective and streamlined.

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ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: Assembly Attributes

clock November 27, 2018 10:01 by author Peter

I have listed down some of the assembly attributes.

    [assembly: AssemblyKeyFile(@"key.snk")] 
    [assembly: InternalsVisibleTo("System.Numerics, PublicKey=00000000000000000400000000000000", AllInternalsVisible=false)] 
    [assembly: Debuggable(DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints)] 
    [assembly: AssemblyDelaySign(true)] 
    [assembly: InternalsVisibleTo("System, PublicKey=00000000000000000400000000000000", AllInternalsVisible=false)] 
    [assembly: InternalsVisibleTo("System.Core, PublicKey=00000000000000000400000000000000", AllInternalsVisible=false)] 
    [assembly: AllowPartiallyTrustedCallers] 
    [assembly: NeutralResourcesLanguage("en-US")] 
    [assembly: RuntimeCompatibility(WrapNonExceptionThrows=true)] 
    [assembly: Guid("BED7F4EA-1A96-11d2-8F08-00A0C9A6186D")] 
    [assembly: ComCompatibleVersion(1, 0, 0xce4, 0)] 
    [assembly: TypeLibVersion(2, 4)] 
    [assembly: DefaultDependency(LoadHint.Always)] 
    [assembly: StringFreezing] 
    [assembly: ComVisible(false)] 
    [assembly: CLSCompliant(true)] 
    [assembly: CompilationRelaxations(8)] 
    [assembly: SecurityRules(SecurityRuleSet.Level2, SkipVerificationInFullTrust=true)] 
    [assembly: AssemblyTitle("sample.dll")] 
    [assembly: AssemblyDescription("sample.dll")] 
    [assembly: AssemblyDefaultAlias("sample.dll")] 
    [assembly: AssemblyCompany("Microsoft Corporation")] 
    [assembly: AssemblyProduct("Microsoft\x00ae .NET Framework")] 
    [assembly: AssemblyCopyright("\x00a9 Microsoft Corporation.  All rights reserved.")] 
    [assembly: AssemblyFileVersion("4.0.30319.225")] 
    [assembly: AssemblyInformationalVersion("4.0.30319.225")] 
    [assembly: SatelliteContractVersion("4.0.0.0")] 
    [assembly: AssemblyTargetedPatchBand("1.0.21-102")] 
    [assembly: SecurityPermission(SecurityAction.RequestMinimum, SkipVerification=true)] 

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ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: Firebase Cloud Messaging From .Net

clock November 22, 2018 10:05 by author Peter

In developing mobile web backends you might need users to broadcast messages such as push notifications to single or all  mobile subscribers from the cloud using services like Firebase Cloud Messaging (FCM).
 
In this article we will focus on sending push notifications from a .Net application using Firebase.Notification library. This library makes it very easy to send push notifications from Firebase using C#
 
To begin, download the library from Nuget:
    Install-Package Firebase.Notification -Version 1.0.0 

Using the library:
    using (var firebase = new Firebase()) 
    { 
        firebase.ServerKey = "{Your Server Key}"; 
        var id = "{Your Device Id}"; 
        firebase.PushNotifyAsync(id,"Hello","World").Wait(); 
        Console.ReadLine(); 
    }        


Error Handling and Debugging
Trace errors in your output window, all errors from this library will be captured under the category Firebase.Notification for easy debugging,

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ASP.NET Core 2.2.1 Hosting - HostForLIFE.eu :: How .NET Is A Multilingual Framework?

clock November 13, 2018 08:18 by author Peter

An application is said to be multilingual if it can be deployed in many different languages. With .NET, all of the languages including Visual Basic, .NET, C#, and J# compile to a common Intermediate language (IL). This makes all languages interoperable. Microsoft has created Java bytecode, which is a low-level language with a simple syntax, which can be very quickly translated into native machine code.

CLR
.NET Framework is a multilingual application because of CLR.CLR is the key of .NET Framework. The code running under the control of the CLR is often termed as managed code.The main task of CLR is to convert compiled code into the native code. .NET Framework has one or more compilers; for e.g., VB .NET, C#, C++, JScript or any third party compiler such as COBOL.

Anyone of these compilers will convert your source code into Microsoft Intermediate Language (MSIL). The main reason for .NET to be multilingual is that you can compile your code from IL and this compiled code will be interoperable with the code that has been compiled to IL from another language.

It simply means that you can create pages in different languages (like C#, VB .NET, J# etc.) and once all of these pages are compiled they all can be used in a single application. Let us understand this point clearly with an example.

Let us consider a situation where a customer needs an application to be ready in 20 days. For completing the application in 20 days we want 30 developers who all know the specific language but we have 15 developers who know C# and 15 developers who know VB .NET. In this situation, if we don’t use .NET then we need to hire 15 more developers of C# or VB .NET which is a difficult and costly solution. Now, if we use .NET then we can use C# and VB .NET language in the same application. This is possible because once C# code is compiled from IL it becomes interoperable with VB .NET code which is compiled from IL.


Then JIT (Just In Time) of CLR converts this MSIL code into native code using metadata which is then executed by OS.

CLR stands for common language runtime. Common language runtime provides other services like memory management, thread management, remoting, and other security such as CTS and CLS. CLR is a layer between an operating system and .NET language, which uses CTS and CLS to create code.

CTS
CTS stands for the common type system. CTS defines rules that common language runtime follows when we are declaring, using and managing type. CTS deals with the data type. .NET supports many languages and every language has its own data type. One language cannot understand data types of another language. For example: When we are creating an application in C#, we have int and when we are creating an application in VB .NET, we have an integer. Here CTS comes into play --  after the compilation, CTS converts int and integer into the int32 structure.

CLS
CLS stands for common language specification. CLS is a subset of CTS and it declares all the rules and restrictions that all languages under .NET Framework must follow. The language which follows these rules is known as CLS compliant. For example, we can use multiple inheritances in c++ but when we use the same code in C# it creates a problem because C# does not support multiple inheritances. Therefore, CLS restricts multiple inheritances for all language. One other rule is that you cannot have a member with the same name and a different case.

In C# add() and Add() are different because it is case sensitive but a problem arises when we use this code in VB .NET because it is not case-sensitive and it considers add() and Add() as the same.

HostForLIFE.eu ASP.NET Core 2.2.1 Hosting
European best, cheap and reliable ASP.NET hosting with instant activation. HostForLIFE.eu is #1 Recommended Windows and ASP.NET hosting in European Continent. With 99.99% Uptime Guaranteed of Relibility, Stability and Performace. HostForLIFE.eu security team is constantly monitoring the entire network for unusual behaviour. We deliver hosting solution including Shared hosting, Cloud hosting, Reseller hosting, Dedicated Servers, and IT as Service for companies of all size.

 



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