In the middleware I want to return the content of a view (Not redirect to it). In my opinion, I should use the context.Response.WriteAsync(); to achieve it. Now I need to get the html string of the view (Also work with Localizer/Model/ViewData in the view). It seems there is not any tutorial about this. How can I solve it? Thank you.

Hi @melon NG , I want to create a custom 404 page without the app.UseStatusCodePages. To this issue, you can check Response.StatusCode in the Program.cs file (asp.net 6) or Startup.cs file (< asp.net 5), then return custom 404 error message or set the path of the custom error page. For example: if meet the 404 error, change the app.UseStatusCodePages(); as below: //app.UseStatusCodePages(); app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. //context.Request.Path = "/Home/Custom404Error"; //await next(); } }); The result as below: If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. Best regards, Dillion

Your design does not make a lot of sense which is the reason you cannot find any information. In MVC the view engine is responsible for rendering the Razor content into HTML. The results are passed back through middleware. Perhaps you want to log the response or you want to create a custom view engine? Can you explain the use case?

the trick is to register your middleware first. then it can pass a memory stream to the next, and harvest after. simple example: https://exceptionnotfound.net/using-middleware-to-log-requests-and-responses-in-asp-net-core/

How can I get a view as string in middleware?

Accepted answer

Zhi Lv - MSFT 32,141 Reputation points Microsoft Vendor

2022-02-16T08:21:43.79+00:00
Hi @melon NG ,

I want to create a custom 404 page without the app.UseStatusCodePages.

To this issue, you can check Response.StatusCode in the Program.cs file (asp.net 6) or Startup.cs file (< asp.net 5), then return custom 404 error message or set the path of the custom error page. For example: if meet the 404 error, change the app.UseStatusCodePages(); as below:

//app.UseStatusCodePages(); app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. //context.Request.Path = "/Home/Custom404Error"; //await next(); } });

The result as below:

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Best regards,
Dillion
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melon NG 291 Reputation points

2022-02-16T08:51:36.067+00:00

The middleware has the 'context.Response.WriteAsync' method also. I can achieve this in middleware too.

However, now the most important is not how to write it but how to get the html code of the existing view.

If the status code is 404 then return the view A, if the status code is 502 then return the view B.

View A and View B differed from each other so much that I have to separate them into two views.

melon NG 291 Reputation points

2022-02-16T08:52:28.983+00:00

What's more, now I am using asp.net 6. The newest version dotnet.

Zhi Lv - MSFT 32,141 Reputation points Microsoft Vendor

2022-02-16T09:26:33.557+00:00

Hi @melon NG ,

I also using the Asp.net 6.

However, now the most important is not how to write it but how to get the html code of the existing view.

If the status code is 404 then return the view A, if the status code is 502 then return the view B.

You can use the context.Request.Path to set the path of the error page:

For example, in the Home Controller, I create a Custom404Error action, and it will generate a custom 404 view page:

@{ ViewData["Title"] = "Custom404Error"; } <h1>This is Custom 404 Error Page</h1>

Then, in the Program.cs file, use the following code:

app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { //await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. context.Request.Path = "/Home/Custom404Error"; await next(); } });

The result is like this:

Best regards,
Dillion

melon NG 291 Reputation points

2022-02-17T03:56:48.36+00:00

I try to create a blank new asp.net 6 mvc project and add these codes in program.cs:

var builder = WebApplication.CreateBuilder(args); // Add services to the container. builder.Services.AddControllersWithViews(); var app = builder.Build(); app.UseHttpsRedirection(); app.UseStaticFiles(); app.UseRouting(); app.UseAuthorization(); app.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}"); app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { //await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. context.Request.Path = "/Home/Privacy"; await next(); } }); app.Run();

However, it doesn't work any. It will show the default 404 page of the browser. What's wrong with my code?

melon NG 291 Reputation points

2022-02-17T03:59:33.557+00:00

I try to create a blank new asp.net 6 mvc project and add these codes in program.cs:

var builder = WebApplication.CreateBuilder(args); // Add services to the container. builder.Services.AddControllersWithViews(); var app = builder.Build(); app.UseHttpsRedirection(); app.UseStaticFiles(); app.UseRouting(); app.UseAuthorization(); app.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}"); app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { //await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. context.Request.Path = "/Home/Privacy"; await next(); } }); app.Run();

However, it doesn't work any. It will show the default 404 page of the browser.

What's more, the http://localhost:7219//Home/Privacy is accessible. What's wrong with my code?

Zhi Lv - MSFT 32,141 Reputation points Microsoft Vendor

2022-02-17T06:37:59.393+00:00

Hi @melon NG ,

However, it doesn't work any. It will show the default 404 page of the browser.

The issue relates the Middleware order, try to modify your code as below:

var builder = WebApplication.CreateBuilder(args); // Add services to the container. builder.Services.AddControllersWithViews(); var app = builder.Build(); app.UseHttpsRedirection(); app.Use(async (context, next) => { await next(); if (context.Response.StatusCode == 404) { //await context.Response.WriteAsync("404 not found!"); // you can also use the following code to set the path of the custom error page. context.Request.Path = "/Home/Privacy"; await next(); } }); app.UseStaticFiles(); app.UseRouting(); app.UseAuthorization(); app.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}"); app.Run();

What's more, the http://localhost:7219//Home/Privacy is accessible. What's wrong with my code?

By using the above code, if meeting the 404 error, the request redirects to the "Home/Privacy" page, this page will act as the error page, you can use this page to display the error message.

Best regard,
Dillion

melon NG 291 Reputation points

2022-02-17T07:51:44.343+00:00

Thank you so much.
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