add example to modify headers in Minimal APIs (#34666)

* Add documentation for modifying response headers in Minimal APIs

* Add example for Problem result in Minimal APIs

* Update ms.date in minimal-apis.md

* Update ms.date in responses.md

---------

Co-authored-by: Wade Pickett <[email protected]>

Author: timdeschryver

aspnetcore/fundamentals/minimal-apis.md

@@ -5,7 +5,7 @@ description: Provides an overview of minimal APIs in ASP.NET Core
 ms.author: wpickett
 content_well_notification: AI-contribution
 monikerRange: '>= aspnetcore-6.0'
-ms.date: 10/23/2023
+ms.date: 02/07/2024
 uid: fundamentals/minimal-apis
 ai-usage: ai-assisted
 ---
@@ -171,6 +171,22 @@ app.MapGet("/download", () => Results.File("myfile.text"));
 
 [!INCLUDE [results-helpers](~/fundamentals/minimal-apis/includes/results-helpers.md)]
 
+### Modifying Headers
+
+Use the `HttpResponse` object to modify response headers:
+
+```csharp
+app.MapGet("/", (HttpContext context) => {
+    // Set a custom header
+    context.Response.Headers["X-Custom-Header"] = "CustomValue";
+
+    // Set a known header
+    context.Response.Headers.CacheControl = $"public,max-age=3600";
+
+    return "Hello World";
+});
+```
+
 ### Customizing results
 
 Applications can control responses by implementing a custom <xref:Microsoft.AspNetCore.Http.IResult> type. The following code is an example of an HTML result type:

aspnetcore/fundamentals/minimal-apis/9.0-samples/Snippets/Program.cs

@@ -46,7 +46,14 @@ public static void Main(string[] args)
         // <snippet_10>
         app.MapGet("/download", () => Results.File("myfile.text"));
         // </snippet_10>
-
+        // <snippet_12>
+        app.MapGet("/problem", () =>
+        {
+            var extensions = new List<KeyValuePair<string, object?>> { new("test", "value") };
+            return TypedResults.Problem("This is an error with extensions", 
+                                                        extensions: extensions);
+        });
+        // </snippet_12>
         app.Run();
     }
     // <snippet_11>

aspnetcore/fundamentals/minimal-apis/responses.md

@@ -4,7 +4,7 @@ author: brunolins16
 description: Learn how to create responses for minimal APIs in ASP.NET Core.
 ms.author: brolivei
 monikerRange: '>= aspnetcore-7.0'
-ms.date: 06/04/2024
+ms.date: 02/07/2025
 uid: fundamentals/minimal-apis/responses
 ---
 
@@ -146,6 +146,10 @@ The following sections demonstrate the usage of the common result helpers.
 
 The preceding example returns a 500 status code.
 
+#### Problem and ValidationProblem
+
+:::code language="csharp" source="~/fundamentals/minimal-apis/9.0-samples/Snippets/Program.cs" id="snippet_12":::
+
 #### Text
 
 :::code language="csharp" source="~/fundamentals/minimal-apis/9.0-samples/Snippets/Program.cs" id="snippet_08":::
@@ -195,6 +199,22 @@ Here's an example of a filter that uses one of these interfaces:
 
 For more information, see [Filters in Minimal API apps](xref:fundamentals/minimal-apis/min-api-filters) and [IResult implementation types](xref:fundamentals/minimal-apis/test-min-api#iresult-implementation-types).
 
+## Modifying Headers
+
+Use the `HttpResponse` object to modify response headers:
+
+```csharp
+app.MapGet("/", (HttpContext context) => {
+    // Set a custom header
+    context.Response.Headers["X-Custom-Header"] = "CustomValue";
+
+    // Set a known header
+    context.Response.Headers.CacheControl = $"public,max-age=3600";
+
+    return "Hello World";
+});
+```
+
 ## Customizing responses
 
 Applications can control responses by implementing a custom <xref:Microsoft.AspNetCore.Http.IResult> type. The following code is an example of an HTML result type: