13 February 2016

Creating a 404 Rule within ASP.NET CORE MVC

Creating a NotFound / 404 rule within ASP.NET Core is quite simple, and once you've created that you'll be able to create custom error pages for all error status codes.

1. Update the Startup.cs Located at the root of any ASP.NET Core application is the Startup.cs file containing all the necessary bootstrap code.
2. Update the Configure method with the following:

28 lines

 public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory) 
 { 
 
 ... 
 
   if (env.IsDevelopment()) 
   { 
 
     app.UseDeveloperExceptionPage(); 
 
     app.UseBrowserLink(); 
 
   } 
 
   else 
   { 
 
     //redirects all errors given their error code 
 
     app.UseStatusCodePagesWithReExecute("/error/{0}"); 
 
     app.UseApplicationInsightsExceptionTelemetry(); 
 
   }  
 
   ... 
 
 }

The above code will now redirect all errors, e.g. a 404 not found error will get redirected to /error/404. Now we need to setup the routes and controllers to handle these requests.

3. Update the routing rules

We now need a routing rule to handle all the potential error redirects.

Update the routing rules with the following:

25 lines

      ... 
 
 //This routes specifically handles 404 not found requests 
 
 routes.MapRoute( 
 
 name: "Error-404-Route", 
 
 template: "error/404", 
 
 defaults: new { controller = "Error", action = "NotFound" } 
 
 ); 
 
 routes.MapRoute( 
 
 name: "Error-StatusCode-Route", 
 
 template: "error/{statusCode}", 
 
 defaults: new { controller = "Error", action = "InternalServerError" } 
 
 ); 
 
 ...

4. Create an error controller

Create an error controller in a new file ErrorController.cs with the following code, making sure you take any areas into account if applicable

29 lines

 using Microsoft.AspNetCore.Mvc; 
 
 namespace Test.Controllers 
 { 
 
 public class ErrorController : Controller 
 { 
 
   public IActionResult InternalServerError(int statusCode) 
   { 
 
     ... 
 
     return View("~/Views/Error/500.cshtml"); 
 
   } 
 
   public IActionResult NotFound() 
   { 
 
     ... 
 
     return View("~/Views/Error/404.cshtml"); 
 
   }
 
 } 
 
 }

5. Create the associated views

Now we need to create error views for the associated errors, i.e. ~/Views/Error/404.cshtml

<div>404 Not Found<div/>