Mediatr C# (How It Works For Developers)

Introduction to the Mediator Pattern and MediatR

The mediator pattern is a software design pattern that facilitates the interaction between objects in a manner that reduces direct dependencies between them, promoting loose coupling. MediatR provides an unambitious mediator implementation, focusing on simplicity and efficiency in facilitating object communication.

At the heart of the MediatR library is the concept of requests and multiple handlers. At the request point, an object encapsulates the operation or action details, awaiting processing by the MediatR mechanism. Each request is handled by a corresponding handler or handle method, which contains the business logic to execute the request. This structure is particularly useful for implementing the Command Query Responsibility Segregation (CQRS) pattern, where the separation of read and write operations can lead to more maintainable and scalable software architectures.

Installing MediatR in a .NET Core Project using Package Manager Console

To start using MediatR in an ASP.NET Core project, you first need to install the MediatR package. This can be done through the Package Manager Console in Visual Studio with the following command:

Install-Package MediatR

After installing the package, it's necessary to add MediatR to the ASP.NET Core dependency injection container. This is typically done in the Program.cs or Startup.cs file of your web application project, depending on the version of ASP.NET Core you're using. Here's how you can do it in a program with a minimal API presentation layer.

// Initialize a new web application
var builder = WebApplication.CreateBuilder(args);

// Add MediatR to the service container
builder.Services.AddMediatR(typeof(Program).Assembly);

// Build the web application
var app = builder.Build();

// Initialize a new web application
var builder = WebApplication.CreateBuilder(args);

// Add MediatR to the service container
builder.Services.AddMediatR(typeof(Program).Assembly);

// Build the web application
var app = builder.Build();

In the program class, var builder = WebApplication.CreateBuilder(args); initializes the web application, setting the stage for MediatR integration.

Creating Your First MediatR Request and Handler

MediatR requests are simple classes that represent the data needed to perform a specific operation. Here's an example of a request class that represents a command to create a new user.

public class CreateUserCommand : IRequest<int>
{
    public string Name { get; set; }
    public string Email { get; set; }
    public int Id { get; set; }
}

public class CreateUserCommand : IRequest<int>
{
    public string Name { get; set; }
    public string Email { get; set; }
    public int Id { get; set; }
}

In this example, the CreateUserCommand class implements the IRequest interface, indicating that this request expects an integer response, which could represent the ID of the created user.

Next, you need to create a handler for this request. Within each handler, the Handle method is where the request's logic is executed:

public class CreateUserHandler : IRequestHandler<CreateUserCommand, int>
{
    public async Task<int> Handle(CreateUserCommand command, CancellationToken token)
    {
        // Implement logic to create a user here
        // For this example, let's pretend we create a user and return the ID
        return await Task.FromResult(1); // Assume the user's ID is 1
    }
}

public class CreateUserHandler : IRequestHandler<CreateUserCommand, int>
{
    public async Task<int> Handle(CreateUserCommand command, CancellationToken token)
    {
        // Implement logic to create a user here
        // For this example, let's pretend we create a user and return the ID
        return await Task.FromResult(1); // Assume the user's ID is 1
    }
}

[ApiController]
[Route("[controller]")]
public class UsersController : ControllerBase
{
    private readonly IMediator _mediator;

    public UsersController(IMediator mediator)
    {
        _mediator = mediator;
    }

    [HttpPost]
    public async Task<ActionResult<int>> Create(CreateUserCommand command)
    {
        var userId = await _mediator.Send(command);
        return CreatedAtRoute("GetUser", new { id = userId }, command);
    }
}

[ApiController]
[Route("[controller]")]
public class UsersController : ControllerBase
{
    private readonly IMediator _mediator;

    public UsersController(IMediator mediator)
    {
        _mediator = mediator;
    }

    [HttpPost]
    public async Task<ActionResult<int>> Create(CreateUserCommand command)
    {
        var userId = await _mediator.Send(command);
        return CreatedAtRoute("GetUser", new { id = userId }, command);
    }
}

Introduction of IronPDF Library

IronPDF is a C# library designed for .NET developers who need a straightforward way to create, edit, and work with PDF files in their applications without any write concerns. Developers can generate PDFs without engaging with complex APIs by simply converting web pages or HTML code directly into PDF format. IronPDF is not just limited to creating PDFs; it also offers features for editing PDFs, such as adding text, images, and pages, or even filling out and editing forms within PDF documents. Developers can comprehensively work with PDFs, including tasks like merging, splitting, and securing PDF files with passwords and permissions.

IronPDF specializes in converting HTML to PDF preserving original layouts and styles with precision. This makes it ideal for generating PDFs from web-based content like reports, invoices, and documentation. It supports conversion from HTML files, URLs, and even raw HTML strings into PDF files.

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

using IronPdf;

public class PdfGenerator
{
    public void CreatePdfWithMediaInfo(string htmlContent)
    {
        // Insert your License Key here if required
        License.LicenseKey = "License-Key";

        // Initialize the HtmlToPdf renderer
        var renderer = new ChromePdfRenderer();

        // Create an HTML template with media information
        string htmlTemplate = $@"
            <html>
            <head>
                <title>Media Information</title>
            </head>
            <body>
                <h1>Media Details</h1>

                {htmlContent}
            </body>
            </html>";

        // Convert the HTML string to a PDF document
        var pdfDocument = renderer.RenderHtmlAsPdf(htmlTemplate);
        pdfDocument.SaveAs("MediaInformation.pdf");
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Example HTML content with MediatR information
        string htmlContent = @"
            <div>
                <h2>MediatR Information</h2>
                <p>MediatR is a media tracking system...</p>
            </div>";

        // Create an instance of PdfGenerator
        PdfGenerator pdfGenerator = new PdfGenerator();

        // Call the CreatePdfWithMediaInfo method to generate the PDF
        pdfGenerator.CreatePdfWithMediaInfo(htmlContent);

        Console.WriteLine("PDF generated successfully.");
    }
}

using IronPdf;

public class PdfGenerator
{
    public void CreatePdfWithMediaInfo(string htmlContent)
    {
        // Insert your License Key here if required
        License.LicenseKey = "License-Key";

        // Initialize the HtmlToPdf renderer
        var renderer = new ChromePdfRenderer();

        // Create an HTML template with media information
        string htmlTemplate = $@"
            <html>
            <head>
                <title>Media Information</title>
            </head>
            <body>
                <h1>Media Details</h1>

                {htmlContent}
            </body>
            </html>";

        // Convert the HTML string to a PDF document
        var pdfDocument = renderer.RenderHtmlAsPdf(htmlTemplate);
        pdfDocument.SaveAs("MediaInformation.pdf");
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Example HTML content with MediatR information
        string htmlContent = @"
            <div>
                <h2>MediatR Information</h2>
                <p>MediatR is a media tracking system...</p>
            </div>";

        // Create an instance of PdfGenerator
        PdfGenerator pdfGenerator = new PdfGenerator();

        // Call the CreatePdfWithMediaInfo method to generate the PDF
        pdfGenerator.CreatePdfWithMediaInfo(htmlContent);

        Console.WriteLine("PDF generated successfully.");
    }
}

Conclusion

By following the steps outlined in this article, you should now have a solid foundation for incorporating MediatR into your projects, starting from basic command and query handling to leveraging more advanced features like notifications and behaviors. As your application grows and evolves, MediatR offers tools and patterns that can help keep your codebase clean, maintainable, and scalable.

As we conclude, it's worth noting that exploring and integrating different libraries and tools, such as IronPDF, can further enhance your .NET projects. IronPDF offers a free trial of advanced PDF features. For projects requiring advanced PDF features, IronPDF's licensing starts from $799, offering a robust solution for .NET developers looking to extend their application's functionalities.