Add option to ExceptionHandlerMiddleware to choose status code based on exception (#33438)

Author: tdykstra

aspnetcore/fundamentals/error-handling.md

@@ -5,7 +5,7 @@ description: Discover how to handle errors in ASP.NET Core apps.
 monikerRange: '>= aspnetcore-3.1'
 ms.author: tdykstra
 ms.custom: mvc
-ms.date: 05/30/2024
+ms.date: 08/25/2024
 uid: fundamentals/error-handling
 ---
 # Handle errors in ASP.NET Core
@@ -70,6 +70,10 @@ The following code uses a lambda for exception handling:
 
 :::code language="csharp" source="~/fundamentals/error-handling/samples/7.x/ErrorHandlingSample/Snippets/Program.cs" id="snippet_UseExceptionHandlerInline" highlight="5-29":::
 
+Another way to use a lambda is to set the status code based on the exception type, as in the following example:
+
+:::code language="csharp" source="~/fundamentals/error-handling/samples/9.x/ErrorHandlingSample/Program.cs" id="snippet_lambda" highlight="2,6-11":::
+
 > [!WARNING]
 > Do **not** serve sensitive error information to clients. Serving errors is a security risk.
 

aspnetcore/fundamentals/error-handling/samples/9.x/ErrorHandlingSample/ErrorHandlingSample.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

aspnetcore/fundamentals/error-handling/samples/9.x/ErrorHandlingSample/Program.cs

@@ -0,0 +1,45 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Hosting;
+using System;
+using Microsoft.AspNetCore.Diagnostics;
+using static System.Net.Mime.MediaTypeNames;
+
+namespace ErrorHandlingSample
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            
+            //<snippet_lambda>
+            var builder = WebApplication.CreateBuilder(args);
+            builder.Services.AddProblemDetails();
+            var app = builder.Build();
+            if (app.Environment.IsDevelopment())
+            {
+                app.UseExceptionHandler(new ExceptionHandlerOptions
+                {
+                    StatusCodeSelector = ex => ex is TimeoutException
+                        ? StatusCodes.Status503ServiceUnavailable
+                        : StatusCodes.Status500InternalServerError
+                });
+            }
+            //</snippet_lambda>
+            app.MapGet("/", () => "Hello World!");
+
+            app.MapGet("/timeout", () =>
+            {
+                throw new TimeoutException();
+            });
+
+            app.MapGet("/exception", () =>
+            {
+                throw new Exception();
+            });
+
+            app.Run();
+        }
+    }
+}