How can I enable detailed error pages in a staging ASP.NET Core MVC environment?

When running in production or staging, ASP.NET Core intentionally hides detailed errors to avoid exposing sensitive information. By default, the Developer Exception Page (which shows detailed error info) is only enabled when the environment is Development. There are a couple of ways to see detailed errors while running locally with a staging or production environment:

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1. Modify the Middleware Condition

You can update your exception handling code in Startup (or Program in minimal hosting) to enable the Developer Exception Page for the Staging environment locally. For example:

CSHARPCopied
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Allow detailed errors in Development and Staging
    if (env.IsDevelopment() || env.EnvironmentName == "Staging")
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
        // Optionally enforce HSTS in production environments
        app.UseHsts();
    }

    // other middleware registrations
    app.UseHttpsRedirection();
    app.UseStaticFiles();
    app.UseRouting();
    app.UseAuthorization();
    
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapDefaultControllerRoute();
    });
}

With this change, if you run your project locally using the "TestApp-Staging" profile, you’ll be able to see detailed errors.

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2. Use a Custom Flag or Conditional Check

Rather than modifying middleware based solely on the ASPNETCORE_ENVIRONMENT variable, you can also create a custom flag (for example, a configuration setting) to enable detailed errors on localhost even when in production or staging. For example:

CSHARPCopied
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IConfiguration configuration)
{
    bool showDetailedErrorsOnLocalhost = configuration.GetValue<bool>("ShowDetailedErrorsOnLocalhost");

    // Check if the request is from localhost (or any other condition) 
    if (env.IsDevelopment() || (env.EnvironmentName == "Staging" && showDetailedErrorsOnLocalhost))
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
    }

    // Other middleware registrations ...
}

Then, in your local configuration (such as an appsettings.Local.json), you could set "ShowDetailedErrorsOnLocalhost": true so that detailed errors are enabled when debugging locally.

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Recommendations

• Security Considerations: Keep in mind that showing detailed errors can expose sensitive information. Even if you’re debugging locally, ensure this behavior is not accidentally deployed to your public staging or production environments.

• Temporary Changes: If you only need detailed errors temporarily for troubleshooting, remember to revert these changes before deploying.

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By altering your middleware setup as shown above, you can have more flexibility with which environments show detailed error messages, especially when working on a local machine with staging or production settings.