CSharp Web API Concepts

Introduction

This pages is to capture some useful thing around the Web API.

Middleware

I was trying to match up my Typescript work with C# so I started off be looking a middleware. Not a difficult concept. So for .NET 8.0 for me it consisting of

• Making and Extension
• Applying the extension
• Implementing the middleware

Pretty straight forward

// Create an extension
    public static IApplicationBuilder UseCustomMiddleware(this IApplicationBuilder app)
    {
        return app.UseMiddleware<CustomMiddleware>();
    }

// Applying the extension
...
        var app = builder.Build();

        app.UseCustomMiddleware();

        app.MapGet("/", (HttpContext context) =>
        {
            return "Hello World!";
        });
...

// Implementing the middleware
public class CustomMiddleware
{
    private readonly RequestDelegate _next;

    public CustomMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        Console.WriteLine($"Request: {context.Request.Path}");
        await _next(context);
    }
}

Validation of Request

So I implement this with middleware in typescript too but watching youtube has led me to two approaches

• Fluent Validation (3rd party)
• Data Validation (Microsoft

Fluent Validation

Lets install it first

dotnet add package FluentValidation.DependencyInjectionExtensions

Add the service

...
builder.Services.AddValidatorsFromAssemblyContaining<Program>();
...

I am going to valid a request for a vehicle which can have a rego or a responsibility code.