Custom Error Pages in .Net Core

1. Enable Custom Error Pages in Startup.cs

Configure Custom Error Handling Middleware

In your Startup.cs file, configure the error handling middleware to show custom error pages for different status codes (e.g., 404, 500). You’ll typically use the UseStatusCodePagesWithReExecute middleware for custom error pages.

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage(); // Detailed error in development
    }
    else
    {
        // Custom error pages for non-development environments
        app.UseExceptionHandler("/Error/GeneralError");
        app.UseStatusCodePagesWithReExecute("/Error/{0}");
    }

    app.UseStaticFiles(); // Serve static files
    app.UseMvcWithDefaultRoute(); // MVC routing
}

Custom Error Controller

Create an ErrorController that will handle different error types. The {0} in the path passed to UseStatusCodePagesWithReExecute corresponds to the HTTP status code, such as 404 or 500.

public class ErrorController : Controller
{
    public IActionResult GeneralError()
    {
        return View("GeneralError");
    }

    public IActionResult Error404()
    {
        return View("404");
    }

    public IActionResult Error500()
    {
        return View("500");
    }
}

Create the corresponding views under Views/Error for each error page (e.g., 404.cshtml, 500.cshtml, and GeneralError.cshtml).

Example Folder Structure

/Views/Error/
  ├── 404.cshtml
  ├── 500.cshtml
  └── GeneralError.cshtml

Custom Error Handling in appsettings.json (Optional)

You can also configure error settings like showing friendly error pages in appsettings.json:

{
  "CustomErrors": {
    "Enabled": true,
    "DefaultRedirect": "/Error/GeneralError"
  }
}

In Startup.cs, you can read this configuration and set the error pages accordingly.

2. Handle Static File Errors

To ensure custom error pages are shown for static file errors (e.g., missing images or CSS files), you can use the UseStatusCodePagesWithReExecute middleware to catch 404 errors caused by static files as well.

app.UseStatusCodePagesWithReExecute("/Error/{0}");

This will redirect to the appropriate error page based on the HTTP status code, including those caused by static file errors.

Tip: Detailed Error Handling in Development

For local development, you can use the UseDeveloperExceptionPage() to show detailed error information, and in production, use UseExceptionHandler() with a custom error page.

if (env.IsDevelopment())
{
    app.UseDeveloperExceptionPage(); // Show detailed error pages in development
}
else
{
    app.UseExceptionHandler("/Error/GeneralError"); // Show a general error page in production
}

Summary

So to clarify: