Add minimal API sample of reading the request stream (#24327)

Co-authored-by: Luke Latham <1622880+guardrex@users.noreply.github.com>
Co-authored-by: Stephen Halter <halter73@gmail.com>

aspnetcore/fundamentals/minimal-apis.md

@@ -597,6 +597,17 @@ The preceding code:
   }
   ```
 
+### Read the request body
+
+Read the request body directly using a <xref:Microsoft.AspNetCore.Http.HttpContext> or <xref:Microsoft.AspNetCore.Http.HttpRequest> parameter:
+
+[!code-csharp[](minimal-apis/samples/WebMinAPIs/Program.cs?name=snippet_fileupload)]
+
+The preceding code:
+
+* Accesses the request body using <xref:Microsoft.AspNetCore.Http.HttpRequest.BodyReader?displayProperty=nameWithType>.
+* Copies the request body to a local file.
+
 ## Responses
 
 Route handlers support the following types of return values:

aspnetcore/fundamentals/minimal-apis/samples/WebMinAPIs/Program.cs

@@ -813,4 +813,20 @@ app.MapGet("/skipme", () => "Skipping Swagger.")
 app.Run();
 #endregion
 
+#elif FILEUPLOAD
+#region snippet_fileupload
+var builder = WebApplication.CreateBuilder(args);
+var app = builder.Build();
+
+app.MapPost("/uploadstream", async (IConfiguration config, HttpRequest request) =>
+{
+    var filePath = Path.Combine(config["StoredFilesPath"], Path.GetRandomFileName());
+
+    await using var writeStream = File.Create(filePath);
+    await request.BodyReader.CopyToAsync(writeStream);
+});
+
+app.Run();
+#endregion
+
 #endif