Overview

• The exception handling features help us deal with the unforeseen errors which could appear in our code.
• To handle exceptions we can use the try-catch block in our code as well as finally keyword to clean up resources afterward.

Developer Exception Page

• To configure an app to display a page that shows detailed information about exceptions, install the **Microsoft.AspNetCore.Diagnostics** package.
• Put UseDeveloperExceptionPage before any middleware you want to catch exceptions in, such as app.UseMvc.

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
		 app.UseDeveloperExceptionPage();
}

Custom Exception Handling Page

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
		app.UseExceptionHandler("/error");
}

• In an MVC app, don't explicitly decorate the error handler action method with HTTP method attributes, such as HttpGet.
  • Using explicit verbs could prevent some requests from reaching the method.

[Route("/Error")]
public IActionResult Index()
{
    // Handle error here
}

Configuring Status Code Pages

• By default, an app doesn't provide a rich status code page for HTTP status codes, such as 404 Not Found.
• To provide status code pages, configure the Status Code Pages Middleware by adding a line to the Startup.Configure method:

app.UseStatusCodePages();

• By default, Status Code Pages Middleware adds simple, text-only handlers for common status codes, such as 404.
• The middleware supports several extension methods. One method takes a lambda expression:

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

• Another method takes a content type and format string:

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