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This article mainly introduces the relevant knowledge of "how to deal with the error environment in ASP.NET Core". The editor shows you the operation process through the actual case. The operation method is simple, fast and practical. I hope this article "how to deal with the error environment in ASP.NET Core" can help you solve the problem.

1. Preface

ASP.NET Core can be divided into two types of error environments: development environment and non-development environment.

Development environment: developer exception page.

Non-development environment: exception handler page, status code page.

We will see the following code in the Startup.Configure method:

Public void Configure (IApplicationBuilder app, IHostingEnvironment env) {if (env.IsDevelopment ()) {/ / Development Environment} else {/ / non-development Environment}

Env.IsDevelopment () is to determine whether the application is running in the development environment or non-development environment. The specific configuration is in Properties/launchSettings.json, and the ASPNETCORE_ENVIRONMENT attribute is found. The default value is the development environment (Development). We will learn about the specific environment configuration knowledge later.

two。 Developer exception page

Add code to the Startup.Configure method to enable this page when the application is running in the development environment:

If (env.IsDevelopment ()) {app.UseDeveloperExceptionPage ();}

Developer exception pages are enabled only when the application is running in the development environment, and calling UseDeveloperExceptionPage is configured in front of any middleware whose exceptions you want to catch.

This page includes the following information about exceptions and requests:

Stack trace

Query string parameters (if any)

Cookie (if any)

Request header

3. Exception handler page

In the following example, UseExceptionHandler adds exception handling middleware in a non-development environment:

If (env.IsDevelopment ()) {app.UseDeveloperExceptionPage ();} else {app.UseExceptionHandler ("/ Error"); app.UseHsts ();}

The Razor Pages application template provides Error pages (.cshtml) and PageModel classes (ErrorModel) in the pages folder. For MVC applications, the project template includes Error action methods and Error views. The method of operation is as follows:

[AllowAnonymous] [ResponseCache (Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)] public IActionResult Error () {return View (new ErrorViewModel {RequestId = Activity.Current?.Id?? HttpContext.TraceIdentifier);}

Do not use HTTP method properties, such as HttpGet, to decorate the error handler's operation methods, as some methods that request access are blocked. It is also best to allow anonymous access to the method so that unauthenticated users can receive the wrong view.

You can also use lambda for exception handling in UseExceptionHandler:

If (env.IsDevelopment ()) {app.UseDeveloperExceptionPage ();} else {app.UseExceptionHandler (errorApp = > {errorApp.Run (async context = > {context.Response.StatusCode = 500; context.Response.ContentType = "text/html"; await context.Response.WriteAsync ("\ r\ n"); await context.Response.WriteAsync ("ERROR!

\ r\ n "); var exceptionHandlerPathFeature = context.Features.Get (); / / Use exceptionHandlerPathFeature to process the exception (for example, / / logging), but do NOT expose sensitive error information directly to / / the client. If (exceptionHandlerPathFeature?.Error is FileNotFoundException) {await context.Response.WriteAsync (" File error thrown!

\ r\ n ");} await context.Response.WriteAsync (" Home ")

\ r\ n "); await context.Response.WriteAsync ("\ r\ n "); await context.Response.WriteAsync (new string (', 512)); / / IE padding});}); app.UseHsts ();} 4. Status code page

In general, ASP.NET Core applications do not provide a status code page for HTTP status codes such as "404-not found". However, to provide a status code page, you can use the status code page middleware.

4.1 UseStatusCodePages middleware

To enable the default plain text handler for common error status codes, call UseStatusCodePages in the Startup.Configure method:

App.UseStatusCodePages ()

One thing to note here is that invoking UseStatusCodePages middleware is called before middleware such as static file middleware and MVC middleware:

App.UseStatusCodePages (); app.UseStaticFiles (); app.UseMvc (routes = > {routes.MapRoute (name: "default", template: "{controller=Home} / {action=Index} / {id?}");})

Let's see the effect of configuring the middleware by running the application and entering a non-existent address on the browser address bar:

Obviously, when we enter a non-existent address, we open a status code page that handles errors.

UseStatusCodePages middleware also has two methods of overloading, so the specific running results will not be screenshots, and we will test them by ourselves.

UseStatusCodePages that contains the format string:

App.UseStatusCodePages ("text/plain", "Status code page, status code: {0}")

UseStatusCodePages containing lambda:

App.UseStatusCodePages (async context = > {context.HttpContext.Response.ContentType = "text/plain"; await context.HttpContext.Response.WriteAsync ("Status code page, status code:" + context.HttpContext.Response.StatusCode);}); 4.2 UseStatusCodePagesWithRedirect middleware

Send the 302-found status code to the client.

Redirect the client to a location in the URL template.

Let's call UseStatusCodePagesWithRedirect in the Startup.Configure method:

App.UseStatusCodePagesWithRedirects ("/ Error/ {0}")

Run the application and enter the non-existent address https://localhost:44353/1 on the browser to see the effect of configuring the middleware. You will find that when we enter the above address, we will jump to the https://localhost:44353/Error/404 link and display:

This makes it clear that when we enter an address that does not exist, we will redirect the middleware settings to the address page.

This is the end of the introduction to "how ASP.NET Core handles the wrong environment". Thank you for reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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