July 29, 2024 07:51 by
PeterWeb applications frequently need to generate PDF documents on the fly, whether they be invoices, certifications, reports, or some other kind of document. We'll go over how to use the iText7 library to generate PDFs in a.NET Core Web API in this tutorial. To illustrate how to generate a certificate PDF, we will develop a sample project.
Step 1: Create a project for your.NET Core Web API
Make a new project for a web API
To start a new Web API project, open a terminal or command prompt and type the following command.
dotnet new webapi -n PdfGenerationDemo
cd PdfGenerationDemo
Install Necessary NuGet packages
We will use iText7 for PDF generation. Install it using the following command.
dotnet add package itext7
Step 2. Create Your Models
Create a model to represent the data needed for the certificate. Add a new class CertificateModel.cs in the Models folder.
namespace PdfGenerationDemo.Models
{
public class CertificateModel
{
public string Full_Name { get; set; }
public string University_Name { get; set; }
public string Mobile_Number { get; set; }
public string Email { get; set; }
public string CampName { get; set; }
public string From_Date { get; set; }
public string To_Date { get; set; }
public string Description { get; set; }
public string Duration { get; set; }
public string Institute_Name { get; set; }
public string Nss_Logo { get; set; }
public string ProfileImageBase64 { get; set; }
}
}
Step 3. Create Your Controller
Add a new controller CertificateController.cs in the Controllers folder.
using Microsoft.AspNetCore.Mvc;
using PdfGenerationDemo.Models;
using System;
using System.IO;
using System.Threading.Tasks;
using iText.Html2pdf;
using iText.Kernel.Pdf;
namespace PdfGenerationDemo.Controllers
{
[Route("api/[controller]")]
[ApiController]
public class CertificateController : ControllerBase
{
[HttpPost]
[Route("GenerateCertificate")]
public async Task<IActionResult> GenerateCertificate([FromBody] CertificateModel request)
{
if (request == null)
{
return BadRequest("Invalid request data.");
}
try
{
byte[] pdfBytes = GeneratePDF(request);
string base64String = Convert.ToBase64String(pdfBytes);
return Ok(new { Success = true, PdfBase64 = base64String });
}
catch (Exception ex)
{
return StatusCode(500, $"Internal server error: {ex.Message}");
}
}
private byte[] GeneratePDF(CertificateModel request)
{
string body = Template_Body(request);
using (MemoryStream outputStream = new MemoryStream())
{
PdfWriter writer = new PdfWriter(outputStream);
PdfDocument pdfDoc = new PdfDocument(writer);
pdfDoc.SetDefaultPageSize(iText.Kernel.Geom.PageSize.A4);
HtmlConverter.ConvertToPdf(body, pdfDoc);
return outputStream.ToArray();
}
}
private string Template_Body(CertificateModel request)
{
string logoBase64 = request.Logo;
string photoBase64 = Convert.ToBase64String(Convert.FromBase64String(request.ProfileImageBase64));
return $@"
<html>
<head>
<style type='text/css'>
body, html {{
margin: 0;
padding: 0;
width: 100%;
height: 100%;
font-family: Georgia, serif;
}}
.container {{
border: 15px solid #888;
width: 90%;
margin: 0 auto;
padding: 20px;
background-color: white;
box-shadow: 0 0 10px rgba(0,0,0,0.5);
text-align: center;
}}
.logo img {{
width: 300px;
margin-bottom: 15px;
}}
.marquee {{
color: tan;
font-size: 36px;
margin: 10px 0;
}}
.assignment {{
font-size: 20px;
margin: 20px 0;
}}
.person {{
border-bottom: 2px solid black;
font-size: 24px;
font-style: italic;
margin: 20px auto;
width: 80%;
display: inline-block;
}}
.details {{
font-size: 18px;
margin: 20px 0;
}}
.photo img {{
border: 1px solid #ddd;
border-radius: 100%;
padding: 0px;
width: 150px;
}}
.reason {{
margin: 20px 0;
font-size: 18px;
}}
.signature {{
margin-top: 50px;
font-size: 18px;
}}
.signature .sig-line {{
border-bottom: 1px solid black;
width: 50%;
margin: 20px auto;
}}
.footer {{
font-size: 14px;
color: #aaa;
margin-top: 30px;
}}
</style>
</head>
<body>
<div class='container'>
<div class='logo'>
<img src='data:image/png;base64,{logoBase64}' alt='Logo'>
</div>
<div class='marquee'>
Certificate of NSS
</div>
<div class='assignment'>
{request.University_Name}
</div>
<div class='assignment'>
This certificate is presented to
</div>
<div class='photo'>
<img src='data:image/jpeg;base64,{photoBase64}' alt='Student Photo'>
</div>
<div class='person'>
{request.Full_Name}
</div>
<div class='details'>
<p>Number: {request.Mobile_Number}</p>
<p>Email: {request.Email}</p>
<p>Camp Name: {request.CampName}</p>
<p>Camp Time: {request.From_Date} To {request.To_Date}</p>
<p>Description: {request.Description}</p>
</div>
<div class='reason'>
For Participation in Camp of {request.Duration} With College<br />
</div>
<div class='reason'>
{request.Institute_Name}<br />
</div>
<div class='signature'>
<p>Authorized Signature</p>
<div class='sig-line'></div>
</div>
<div class='footer'>
<p>© 2024 An Organization. All Rights Reserved.</p>
</div>
</div>
</body>
</html>";
}
}
}
Step 4. Testing the API
You can test the API using a tool like Postman. Here’s how you can do it.
Run Your Project
dotnet run
Get the Response
The response will contain a base64 encoded string of the generated PDF.
The response will contain a base64 encoded string of the generated PDF.
Conclusion
We have covered in this post how to use the iText7 library to generate PDFs in a.NET Core Web API. We went through how to set up the project, write the controller, create models, and test the API. This method can be expanded upon and altered to suit different use cases requiring the creation of dynamic PDFs.
July 23, 2024 08:21 by
PeterProviding prompt and efficient communication is essential in the quickly changing digital world of today, particularly for educational platforms and technical blogs that serve programmers, students, and IT professionals. Similar to C# Corner, Codingvila is a technical blog that has made a name for itself as a place where computer enthusiasts can go to get help through tutorials, articles, and community assistance. The implementation of an AI chatbot can transform the way users engage with the platform and improve this support system. In order to provide real-time support and interactive learning opportunities, the "Codingvila Chatbot" makes use of.NET Core.
Why a Chatbot?
- Instant Support: A chatbot can provide immediate answers to common queries, reducing wait times and improving user satisfaction.
- Scalability: As the user base grows, a chatbot can effortlessly handle multiple queries at once, unlike human counterparts.
- 24/7 Availability: It offers round-the-clock support, crucial for users in different time zones or those working on projects outside typical office hours.
- Personalized Learning: The chatbot can recommend articles and tutorials based on the user's past interactions and preferences.
- Community Engagement: By handling routine questions, the chatbot allows community managers to focus on more complex queries and community-building activities.
Setting Up the Project
Ensure you have the .NET Core SDK installed to begin. Set up a new project using the command line.
dotnet new console -n HostforlifeChatbot
cd HostforlifeChatbot
This creates a basic .NET Core console application which serves as the foundation for our chatbot.
Integrating Microsoft Bot Framework
Utilize Microsoft's Bot Framework for robust chatbot functionalities. Install the necessary packages.
dotnet add package Microsoft.Bot.Builder
dotnet add package Microsoft.Bot.Builder.Integration.AspNet.Core
These tools enable the use of advanced features like dialogues and conversation flows, essential for an interactive chatbot.
Creating the Bot
1. Bot Framework Setup
Implement the HostforlifeBot.cs to manage interactions.
using Microsoft.Bot.Builder;
using Microsoft.Bot.Schema;
using System.Threading.Tasks;
public class HostforlifeBot : IBot
{
public async Task OnTurnAsync(ITurnContext turnContext, CancellationToken cancellationToken = default)
{
if (turnContext.Activity.Type == ActivityTypes.Message)
{
string userInput = turnContext.Activity.Text;
string response = ProcessInput(userInput);
await turnContext.SendActivityAsync(MessageFactory.Text(response), cancellationToken);
}
}
private string ProcessInput(string input)
{
if (input.Contains("hello"))
{
return "Hello! Welcome to Hostforlife.com, How can I assist you today?";
}
else if (input.Contains("help"))
{
return "Here are some things you can ask me...";
}
else
{
return "I'm not sure how to help with that, but I'm learning more every day!";
}
}
}
2. Configure Services and Middleware
Adjust Startup.cs to set up services for the bot.
public void ConfigureServices(IServiceCollection services)
{
services.AddBot<HostforlifeBot>(options =>
{
options.State.Add(new ConversationState(new MemoryStorage()));
});
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseDefaultFiles();
app.UseStaticFiles();
app.UseBotFramework();
}
Running the Chatbot
Execute the application
dotnet run
Your chatbot, "Hostforlife Chatbot" is now operational locally. It can be extended to support various platforms like Microsoft Teams, Slack, or Facebook Messenger.
Summary
The Hostforlife Chatbot, developed with .NET Core and Microsoft Bot Framework, is designed to enhance the educational resources of Hostforlife by providing an interactive, responsive, and engaging user experience. This AI-driven tool not only supports real-time communication but also encourages an interactive learning environment, making technology more accessible and comprehensible to its audience.
July 17, 2024 08:49 by
PeterWeb application security relies heavily on authentication and authorization to make sure users are who they say they are and to control what actions they can do. Robust means for integrating authorization and authentication into your apps are provided by ASP.NET Core. We'll go into great detail about these ideas in this post, including key elements, recommended procedures, and real-world application examples.
Understanding Authentication and Authorization
Authentication verifies the identity of users attempting to access your application. It answers the question, "Who are you?" Common authentication methods include.
- Cookie-based Authentication: Uses encrypted cookies to authenticate users.
- Token-based Authentication: Utilizes JWT (JSON Web Tokens) or OAuth tokens for authentication.
- External Authentication Providers: Allows users to log in using external providers like Google, Facebook, etc.
- Windows Authentication: Uses Windows credentials for intranet applications.
Authorization, on the other hand, determines what authenticated users are allowed to do within the application. It answers the question, "What are you allowed to do?" Authorization can be role-based, policy-based, or claim-based, where.
Role-based Authorization: Assigns roles (admin, user, manager) to users and restricts access based on roles.
Policy-based Authorization: Defines access policies that evaluate a combination of roles, claims, and requirements.
Claim-based Authorization: Grants access based on specific claims associated with the user's identity.
Implementing Authentication in ASP.NET Core
Cookie Authentication: Cookie authentication is commonly used for web applications that require user sessions. ASP.NET Core provides built-in middleware to handle cookie-based authentication.
// Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
.AddCookie(options =>
{
options.Cookie.Name = "YourAppCookie";
options.LoginPath = "/Account/Login";
options.AccessDeniedPath = "/Account/AccessDenied";
});
}
Token-based Authentication: Token-based authentication is suitable for APIs and single-page applications (SPA). ASP.NET Core supports JWT (JSON Web Tokens) authentication out of the box.
// Startup.cs
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"]))
};
});
}
Implementing Authorization in ASP.NET Core: Authorization is configured using policies and requirements. Define policies in Startup.cs and apply them using the [Authorize] attribute in controllers or actions.
// Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddAuthorization(options =>
{
options.AddPolicy("AdminOnly", policy => policy.RequireRole("Admin"));
options.AddPolicy("MinimumAge", policy =>
policy.Requirements.Add(new MinimumAgeRequirement(18)));
});
}
// Controller
[Authorize(Policy = "AdminOnly")]
public IActionResult AdminDashboard()
{
return View();
}
Summary
In this article, we've explored the fundamentals of authentication and authorization in ASP.NET Core. Understanding these concepts is crucial for building secure and scalable web applications. ASP.NET Core provides flexible and powerful tools to implement various authentication and authorization mechanisms tailored to your application's needs. By leveraging these capabilities effectively, you can ensure that your application remains secure and compliant with modern security standards.
Implementing authentication and authorization involves configuring middleware, defining policies, and applying attributes correctly across your application. Whether you choose cookie-based authentication for web applications or token-based authentication for APIs, ASP.NET Core offers comprehensive support and flexibility to meet your security requirements.
By following best practices and staying updated with the latest security trends, you can build robust and secure ASP.NET Core applications that protect user data and maintain user trust.
July 9, 2024 07:09 by
PeterAsynchronous programming in C# frequently entails doing several tasks at once. Task and Split are two popular approaches to managing many tasks.Task.WhenAll and WaitAll. Despite their apparent similarities, they have different functions and are employed in various contexts. The distinctions between Task.WaitAll and Task.WhenAll are examined in this article, along with real-world examples to show how to use both.
What is Task.WaitAll?
Assignment.The synchronous function WaitAll stops the calling thread after each of the supplied tasks is finished. It's helpful when you have to make sure that a group of tasks is completed before moving on, but it does so in a blocking way, meaning that Task is called by the thread.Until every task is completed, WaitAll is in use.
Example Usage of Task.WaitAll
using System;
using System.Threading.Tasks;
class Program
{
static void Main()
{
Task task1 = Task.Run(() => PerformTask(1));
Task task2 = Task.Run(() => PerformTask(2));
Task task3 = Task.Run(() => PerformTask(3));
Task.WaitAll(task1, task2, task3); // Blocks until all tasks complete
Console.WriteLine("All tasks completed.");
}
static void PerformTask(int taskId)
{
Console.WriteLine($"Task {taskId} starting.");
Task.Delay(1000).Wait(); // Simulate work
Console.WriteLine($"Task {taskId} completed.");
}
}
In this example, Task.WaitAll blocks the main thread until all three tasks are complete.
What is Task.WhenAll?
Task.WhenAll is an asynchronous method that returns a single task that is completed when all the provided tasks have been completed. Unlike Task.WaitAll, it does not block the calling thread. Instead, it allows the calling code to continue executing asynchronously.
Example Usage of Task.WhenAll
using System;
using System.Threading.Tasks;
class Program
{
static async Task Main()
{
Task task1 = Task.Run(() => PerformTask(1));
Task task2 = Task.Run(() => PerformTask(2));
Task task3 = Task.Run(() => PerformTask(3));
await Task.WhenAll(task1, task2, task3); // Waits for all tasks to complete asynchronously
Console.WriteLine("All tasks completed.");
}
static void PerformTask(int taskId)
{
Console.WriteLine($"Task {taskId} starting.");
Task.Delay(1000).Wait(); // Simulate work
Console.WriteLine($"Task {taskId} completed.");
}
}
In this example, Task.WhenAll allows the main method to await the completion of all tasks without blocking the calling thread.
Key Differences
Blocking vs. Non-blocking
- Task.WaitAll: Blocks the calling thread until all tasks are complete.
- Task.WhenAll: Returns a task that can be awaited, allowing the calling thread to continue execution asynchronously.
Return Type
- Task.WaitAll: Does not return a value.
- Task.WhenAll: Returns a Task that represents the completion of all provided tasks.
Usage Scenario
- Task.WaitAll: Used when you need to block until tasks are complete, typically in non-UI or console applications.
- Task.WhenAll: Used in asynchronous programming, especially in UI applications where blocking the main thread is undesirable.
Practical Use Cases
When to Use Task.WaitAll
- In console applications where you need to ensure that certain tasks are completed before moving on.
- When you are dealing with legacy code that doesn’t support async/await patterns.
When to Use Task.WhenAll
- In UI applications keep the interface responsive.
- In web applications handle multiple asynchronous operations without blocking the main thread.
Conclusion
Task.WaitAll and Task.WhenAll are essential tools in C# for handling multiple tasks. Use Task.WaitAll when you need to block the calling thread until tasks are complete, and Task.WhenAll for asynchronous waiting. Understanding their differences and appropriate use cases can help you write more efficient and responsive applications.
July 2, 2024 08:16 by
PeterCreating robust APIs is more important than ever in the age of modern web development, especially with all these third-party integration we rely on. In this Blog, We will be guiding you how to introduce resilience in. Create an HTTP Client in a. Extensions. Http. Resilience library. In this section, we will take a look at features like setting up retry policies with exponential backoff and timeouts to make your API more resilient against the transient faults.
Step 1. Create a new. NET 8 Web API project Step First, if you have no existing Project then create new with. NET CLI dotnet new web or starting with the default Web API template.
Step 2. Install the Microsoft.AspNetCore. Extensions. Http. Resilience library via NuGet:
dotnet add package Microsoft.Extensions.Http.Resilience --version 8.0.0
Step 3. Configure Resilience in Program.cs
Modify the Program.cs file to set up HttpClient with resilience policies provided by Microsoft.Extensions.Http.Resilience. Here, we will define retry policies and timeouts.
//Add resilience pipeline
builder.Services.AddResiliencePipeline("default", x =>
{
x.AddRetry(new Polly.Retry.RetryStrategyOptions
{
ShouldHandle = new PredicateBuilder().Handle<Exception>(),
Delay = TimeSpan.FromSeconds(2),
MaxRetryAttempts = 2,
BackoffType = DelayBackoffType.Exponential,
UseJitter = true
})
.AddTimeout(TimeSpan.FromSeconds(30));
});
Step 4. Use the Resilient HttpClient in a Service
Next, we'll inject and use the configured HttpClient in your Service. This example shows how to fetch data from an external API using the resilient HttpClient.
public class WeatherService
{
private readonly HttpClient _httpClient;
private readonly ResiliencePipelineProvider<string> _resiliencePipelineProvider;
public WeatherService(HttpClient httpClient,
ResiliencePipelineProvider<string> resiliencePipelineProvider)
{
_httpClient = httpClient;
_resiliencePipelineProvider = resiliencePipelineProvider;
}
public async Task<string> GetWeatherAsync()
{
var pipeline = _resiliencePipelineProvider.GetPipeline("default");
var response = await pipeline
.ExecuteAsync( async ct=> await _httpClient.GetAsync($"https://localhost:7187/weatherforecast",ct));
return await response.Content.ReadAsStringAsync();
}
}
Step 5. Add the endpoint in the Program.cs
app.MapGet("/weatherService/weather", async (WeatherService weatherService) =>
{
var result = await weatherService.GetWeatherAsync();
return result;
})
.WithName("GetWeather")
.WithOpenApi();
Step 6. Run the Application
Finally, run your application and navigate to the endpoint to see the resilient HttpClient in action.
References
Please refer to the below links for more details.
- Building resilient cloud services with .NET 8
- Learning from Microsoft
Conclusion
By following these steps, you have integrated resilience into your .NET 8 Web API project using Microsoft.Extensions.Http.Resilience library. The retry policies, circuit breaker settings, and timeouts will help ensure your API is robust against transient faults, improving its reliability and user experience.