Middleware is the unsung hero of ASP.NET Core apps. It is critical in processing HTTP requests and responses, allowing developers to shape the flow of data in a flexible and orderly manner. In this post, we will take a tour through the diverse terrain of designing middleware in.NET Core, demonstrating real-time examples for a better understanding.

The Middleware Landscape
Middleware in ASP.NET Core serves as a link between the web server and your application. It has the ability to intercept, modify, or even short-circuit the request-response flow. Understanding the various methods for creating middleware is vital for developing powerful web applications.

1. Inline Middleware
The simplest way to create middleware is by defining it inline within the Configure method of your Startup class. Let's consider an example where we want to log incoming requests:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.Use(async (context, next) =>
    {
        // Log the incoming request
        LogRequest(context.Request);
        await next.Invoke();
        // Log the response
        LogResponse(context.Response);
    });
    // Other middleware and app configuration
}

This inline middleware logs both the request and response details for every incoming request.

2. Class-based Middleware
For more organized and reusable middleware, you can create custom middleware classes. Here's an example of a custom middleware class that performs authentication:

public class AuthenticationMiddleware
{
    private readonly RequestDelegate _next;
    public AuthenticationMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task InvokeAsync(HttpContext context)
    {
        // Perform authentication logic
        if (!context.User.Identity.IsAuthenticated)
        {
            context.Response.StatusCode = 401;
            return;
        }
        await _next(context);
    }
}

In the Startup class, register and use this middleware:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseMiddleware<AuthenticationMiddleware>();
    // Other middleware and app configuration
}

3. Middleware Extension Methods
To keep your Startup class clean, you can create extension methods for middleware. Continuing with the authentication example, here's how you can create an extension method:
public static class AuthenticationMiddlewareExtensions
{
    public static IApplicationBuilder UseAuthenticationMiddleware(this IApplicationBuilder app)
    {
        return app.UseMiddleware<AuthenticationMiddleware>();
    }
}

Now, in your Startup class, using this extension method is as simple as:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseAuthenticationMiddleware();
    // Other middleware and app configuration
}

4. Middleware Pipeline Ordering
Order matters in middleware. The sequence in which you add middleware components to the pipeline affects their execution. For instance, if you have middleware that handles error responses, it should be placed after other middleware to catch exceptions.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseExceptionHandler("/Home/Error");  // Error handling middleware
    // Other middleware and app configuration
}

Summary
Middleware is a fundamental part of building robust ASP.NET Core applications. Knowing the various ways to create middleware, from inline methods to class-based and extension methods, empowers you to structure your application's request-response pipeline effectively. By understanding the order of execution in the middleware pipeline, you can ensure that each component plays its role at the right moment. As you continue your journey in ASP.NET Core development, mastering middleware creation will be a valuable skill in your toolkit, enabling you to craft efficient and resilient web applications.

Many applications demand the ability to generate PDF documents programmatically. GrapeCity's GcPdf is a comprehensive library in the.NET ecosystem that allows developers to easily generate, change, and manipulate PDF documents. This blog post will show you how to utilize GcPdf to generate PDF documents programmatically in.NET C#, with actual examples to back it up.

What exactly is GcPdf?
GcPdf is a.NET package that offers extensive PDF document production and manipulation features. It has a variety of features, including:

• Creating PDF documents from the ground up.
• Text, photos, and shapes can be added to PDF pages.
• Changing fonts and styles.
• Making tables and graphs.
• Inserting links and bookmarks.
• Exporting PDFs to various formats.
• Password protection and encryption are being added as security measures.

Let's get started with GcPdf by creating a simple PDF document.

How to Begin with GcPdf?
Make sure you have Visual Studio or your favourite C# development environment installed before we begin. In addition, you must include the GrapeCity Documents for PDF NuGet package (GcPdf) in your project.

Making a Basic PDF Document
In this example, we'll make a simple PDF file with text and a rectangle shape.

using System;
using GrapeCity.Documents.Pdf;
using GrapeCity.Documents.Text;

class Program
{
    static void Main(string[] args)
    {
        // Create a new PDF document
        var doc = new GcPdfDocument();

        // Add a page to the document
        var page = doc.NewPage();

        // Create a graphics object for drawing on the page
        var g = page.Graphics;

        // Add content to the page
        var text = "Hello, World!";
        var font = StandardFonts.Helvetica;
        var fontSize = 24;
        var textFormat = new TextFormat()
        {
            Font = font,
            FontSize = fontSize,
        };

        g.DrawString(text, textFormat, new PointF(100, 100));

        // Create a rectangle
        var rect = new RectangleF(100, 200, 200, 150);
        g.DrawRectangle(rect, Color.Red);

        // Specify the file path where you want to save the PDF
        var filePath = "example.pdf";

        // Save the document to a PDF file
        doc.Save(filePath);

        Console.WriteLine($"PDF created at {filePath}");
    }
}

Explanation of the code

• To represent the PDF document, we construct a new GcPdfDocument object.
• Using doc, add a page to the document.NewPage().
• Make a graphics object (g) to doodle on the page.
• Using g, add text and a rectangle to the page.DrawString() and g.DrawRectangle() are two functions.
• Enter the location to the file where you wish to save the PDF.
• doc Save the document as a PDF file.Save().

After running this code, a PDF file named "example.pdf" will be created in your project directory.

GcPdf Advanced Features
GcPdf has a wide range of tools for creating advanced PDF documents. Here are a few advanced features to look into:

Including Images
Using the g.DrawImage() method, you can add images to your PDF document. This enables you to insert logos, images, or photographs in your documents.

var image = Image.FromFile("logo.png");
g.DrawImage(image, new RectangleF(50, 50, 100, 100));

Making Tables
Tables are widely used to present tabular data in PDF documents. GcPdf includes a Table class that may be used to create tables with a variety of formatting choices.

var table = new Table();
table.DataSource = GetTableData(); // Replace with your data source
page.Elements.Add(table);

Adding Hyperlinks
You can include hyperlinks in your PDFs using the g.DrawString() method with a link destination.
var hyperlinkText = "Visit our website";
var linkDestination = new LinkDestinationURI("https://example.com");
g.DrawString(hyperlinkText, textFormat, new PointF(100, 300), linkDestination);

PDF Security
GcPdf allows you to secure your PDFs by adding passwords or encrypting them. You can set document permissions and control who can view or edit the document.
var options = new PdfSaveOptions
{
    Security = new PdfSecuritySettings
    {
        OwnerPassword = "owner_password",
        UserPassword = "user_password",
        Permissions = PdfPermissions.Print | PdfPermissions.Copy,
    },
};
doc.Save("secure.pdf", options);

Creating customized PDFs for various applications in .NET C# by using GcPdf programmatically is a potent and versatile method. GcPdf offers all the necessary features and flexibility to generate reports, invoices, or other types of documents quickly and efficiently. To enhance your PDF generation capabilities with more in-depth information and examples, please refer to the GcPdf documentation. We wish you happy coding!

Using tools like Swagger/OpenAPI or NSwag to create thorough API documentation for an ASP.NET Core Web API is a critical step in ensuring that your API is well-documented and easy for other developers to understand and utilize. I'll show you how to build API documentation in an ASP.NET Core Web API project using Swagger/OpenAPI in the steps below.

Step 1: Begin by creating an ASP.NET Core Web API Project.
If you do not already have an ASP.NET Core Web API project, you can build one by following the instructions below.

    Start Visual Studio or your favorite code editor.
    Make a new project and select "ASP.NET Core Web Application."
    Choose the "API" template and press "Create."

Step 2: Set up Swashbuckle.AspNetCore
Swashbuckle.AspNetCore is a library that makes integrating Swagger/OpenAPI into your ASP.NET Core Web API project easier. It may be installed using NuGet Package Manager or the.NET CLI.

dotnet add package Swashbuckle.AspNetCore

Step 3. Configure Swagger/OpenAPI
In your Startup.cs file, configure Swagger/OpenAPI in the ConfigureServices and Configure methods.
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using Swashbuckle.AspNetCore.SwaggerUI;

Author: Sardar Mudassar Ali Khan
public void ConfigureServices(IServiceCollection services)
{
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo
        {
            Title = "Auth API",
            Version = "v1",
            Description = "Description of your API",
        });
        var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
        var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
        c.IncludeXmlComments(xmlPath);
    });

}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{

    app.UseSwagger();
    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "Auth API");
        c.RoutePrefix = "api-docs"; // You can change the URL path as needed.
    });

}

Step 4. Add XML Comments
For Swagger to provide descriptions and summaries for your API endpoints, you should add XML comments to your controller methods. To enable XML documentation, go to your project's properties and enable the "Generate XML documentation file" option.

Then, add comments to your controller methods like this:
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using YourNamespace.Models; // Replace with your model namespace
using Microsoft.EntityFrameworkCore;

Author: Peter
[ApiController]
[Route("api/items")]
public class ItemsController : ControllerBase
{
    private readonly YourDbContext _context; // Replace with your DbContext type

    public ItemsController(YourDbContext context)
    {
        _context = context;
    }

    [HttpGet]
    public IActionResult GetItems()
    {
        try
        {
            var items = _context.Items.ToList(); // Assuming "Items" is your DbSet

            if (items == null || items.Count == 0)
            {
                return NoContent(); // Return 204 No Content if no items are found.
            }

            return Ok(items); // Return 200 OK with the list of items.
        }
        catch (Exception ex)
        {
            // Log the exception or handle it accordingly.
            return StatusCode(500, "Internal Server Error"); // Return a 500 Internal Server Error status.
        }
    }
}

Step 5. Run Your API and Access Swagger UI
Build and run your ASP.NET Core Web API project. You can access the Swagger UI by navigating to /api-docs/index.html (or the path you configured in Startup.cs) in your web browser. You should see the API documentation generated by Swagger/OpenAPI.

Now, your ASP.NET Core Web API has comprehensive API documentation generated using Swagger/OpenAPI. Developers can use this documentation to understand and interact with your API effectively.