3. Asp.net core - fundamentals - Middleware ~ BỜM TẬP CODE

3. Asp.net core - fundamentals - Middleware

tháng 8 21, 2021 Không có nhận xét nào

This series is a collection of knowledge about ASP .NET Core. It just is my notes.

Part 1: Startup file.

Part 2: Dependency Injection.

Part 4: Host and Servers.

Part 5: Configurations.

Part 6: Environment.

Part 8: Error Handling.

Part 9: Routing.

Part 10: Make an HTTP Request.

Part 11: Static files.

Part 12: Authentication and Authorization.

This part is to summarise some knowledge concerning the Middleware in Asp .net core.

a. What is middleware

Middleware is software added to the pipeline to process requests and responses.
When a request comes, it goes through one by one middleware (you can think that all middleware do the common process for each request, response)
To use middleware in IApplicationBuilder, use:

Run: param: context
Use: param: context, next -> to invoke next middleware
Map: to branch middleware

We have some built-in middleware, we can use them in configure method.
Of course, we can also create custom middleware.

b. Order of middleware

--> Endpoint middleware to turn the request into an action method in the controller.

c. How to create a custom middleware

step 1: Encapsulate custom middleware in class

Convention: {Name}Middleware
Include:

a constructor with parameter type is "ContextDelegate".
A public method is named Invoke or InvokeAsync. This method must:

Return a Task.
Accept the first parameter of type HttpContext.
Additional parameters for the constructor and Invoke/InvokeAsync are populated by dependency injection (DI).

For example:

public class CustomMiddleware 
{ 
    private readonly RequestDelegate _next; 
    public CustomMiddleware(RequestDelegate next) 
    { 
        _next = next; 
    } 
    // IMyScopedService is injected into Invoke 
    public async Task Invoke(HttpContext httpContext, IMyScopedService svc) 
    { 
        svc.MyProperty = 1000; 
        await _next(httpContext); 
    } 
}

step 2: create a middleware extension method through IApplicationBuilder:

Name convention: Use{MiddlewareName}

using Microsoft.AspNetCore.Builder; 
namespace Culture 
{ 
    public static class RequestCultureMiddlewareExtensions 
    { 
        public static IApplicationBuilder UseRequestCulture( 
            this IApplicationBuilder builder) 
        { 
            return builder.UseMiddleware<RequestCultureMiddleware>(); 
        } 
    } 
}

step 3: Call middleware in Configure method

public class Startup 
{ 
    public void Configure(IApplicationBuilder app) 
    { 
        app.UseRequestCulture(); 
        app.Run(async (context) => 
        { 
            await context.Response.WriteAsync( 
                $"Hello {CultureInfo.CurrentCulture.DisplayName}"); 
        }); 
    } 
}

References:

[Microsoft Learn] - ASP.NET Core Middleware

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