Min API: Add IProblemDetailsService content plus app example (#35982)

* Min API: Add IProblemDetailsService content plus app sample

* Re-organizing sections in minimal-apis.md

* Apply suggestions from code review

Added great suggestions from Mike.

Co-authored-by: Mike Kistler <[email protected]>

* Update aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/Program.cs

Co-authored-by: Mike Kistler <[email protected]>

* Apply suggestions from code review

Added Mike's suggestion: Replace feature with name of feature.

Co-authored-by: Mike Kistler <[email protected]>

* Update aspnetcore/fundamentals/minimal-apis/responses.md

---------

Co-authored-by: Mike Kistler <[email protected]>

Author: wadepickett

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: 05/20/2025
+ms.date: 08/22/2025
 uid: fundamentals/minimal-apis
 ai-usage: ai-assisted
 ---
@@ -56,7 +56,7 @@ The following sections cover request handling: routing, parameter binding, and r
 
 ## Routing
 
-A configured `WebApplication` supports `Map{Verb}` and <xref:Microsoft.AspNetCore.Builder.EndpointRouteBuilderExtensions.MapMethods%2A> where `{Verb}` is a camel-cased HTTP method like `Get`, `Post`, `Put` or `Delete`:
+A configured `WebApplication` supports `Map{Verb}` and <xref:Microsoft.AspNetCore.Builder.EndpointRouteBuilderExtensions.MapMethods%2A> where `{Verb}` is a camel-cased HTTP method like `Get`, `Post`, `Put`, or `Delete`:
 
 [!code-csharp[](~/fundamentals/minimal-apis/7.0-samples/WebMinAPIs/Program.cs?name=snippet_r1)]
 
@@ -112,6 +112,17 @@ app.MapPost("/products",
         => TypedResults.Ok(productId))
     .DisableValidation();
 ```
+### Customize validation error responses using IProblemDetailsService
+
+Customize error responses from minimal API validation logic with an <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> implementation. Register this service in your application's service collection to enable more consistent and user-specific error responses. Support for minimal API validation was introduced in ASP.NET Core in .NET 10.
+
+To implement custom validation error responses:
+
+* Implement <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> or use the default implementation
+* Register the service in the DI container
+* The validation system automatically uses the registered service to format validation error responses
+
+For more information on customizing validation error responses with IProblemDetailsService, see <xref:fundamentals/minimal-apis/responses#customize-validation-error-responses-using-iproblemdetailsservice>.
 
 ## Responses
 

aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/MinApiIproblemDetailsService.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/Program.cs

@@ -0,0 +1,57 @@
+// <snippet_register_IProblemDetailsService_implementation>
+using System.ComponentModel.DataAnnotations;
+
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddProblemDetails(options =>
+{
+    options.CustomizeProblemDetails = context =>
+    {
+        if (context.ProblemDetails.Status == 400)
+        {
+            context.ProblemDetails.Title = "Validation error occurred";
+            context.ProblemDetails.Extensions["support"] = "Contact [email protected]";
+            context.ProblemDetails.Extensions["traceId"] = Guid.NewGuid().ToString();
+        }
+    };
+});
+// </snippet_register_IProblemDetailsService_implementation>
+
+builder.Services.AddValidation();
+
+var app = builder.Build();
+
+app.UseHttpsRedirection();
+
+// Define endpoints
+app.MapGet("/", () => "Hello! Use /products endpoint to test validation with IProblemDetailsService");
+
+// Products endpoint that demonstrates validation
+app.MapPost("/products", (Product product) => 
+{
+    // If validation passes (handled automatically based on DataAnnotations)
+    return TypedResults.Ok(product);
+});
+
+// Explicitly trigger validation failure for testing
+app.MapGet("/products/test-validation-error", () => 
+{
+    // Manually create an invalid product to see the validation error
+    return TypedResults.ValidationProblem(new Dictionary<string, string[]>
+    {
+        { "Name", new[] { "The Name field is required." } },
+        { "Price", new[] { "The field Price must be between 1 and 100." } }
+    });
+});
+
+app.Run();
+
+// Model with validation attributes
+public class Product
+{
+    [Required(ErrorMessage = "The Name field is required.")]
+    public string? Name { get; set; }
+
+    [Range(1, 100, ErrorMessage = "The field Price must be between 1 and 100.")]
+    public decimal Price { get; set; }
+}

aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/TestIProblemDetailsService.http

@@ -0,0 +1,33 @@
+@HostAddress = https://localhost:7134
+
+### Test the home endpoint
+GET {{HostAddress}}
+
+### Test products endpoint with valid data
+POST {{HostAddress}}/products
+Content-Type: application/json
+
+{
+  "name": "Test Product",
+  "price": 50
+}
+
+### Test products endpoint with invalid data (missing name)
+POST {{HostAddress}}/products
+Content-Type: application/json
+
+{
+  "price": 50
+}
+
+### Test products endpoint with invalid data (price out of range)
+POST {{HostAddress}}/products
+Content-Type: application/json
+
+{
+  "name": "Test Product",
+  "price": 200
+}
+
+### Test explicit validation error endpoint
+GET {{HostAddress}}/products/test-validation-error

aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

aspnetcore/fundamentals/minimal-apis/responses.md

@@ -4,8 +4,9 @@ author: brunolins16
 description: Learn how to create responses for minimal APIs in ASP.NET Core.
 ms.author: brolivei
 monikerRange: '>= aspnetcore-7.0'
-ms.date: 05/09/2025
+ms.date: 08/22/2025
 uid: fundamentals/minimal-apis/responses
+ai-usage: ai-assisted
 ---
 
 # How to create responses in Minimal API apps
@@ -154,6 +155,24 @@ The preceding example returns a 500 status code.
 
 :::code language="csharp" source="~/fundamentals/minimal-apis/9.0-samples/Snippets/Program.cs" id="snippet_12":::
 
+#### Customize validation error responses using IProblemDetailsService
+
+Customize error responses from minimal API validation logic with an <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> implementation. Register this service in your application's service collection to enable more consistent and user-specific error responses. Support for minimal API validation was introduced in ASP.NET Core in .NET 10.
+
+To implement custom validation error responses:
+
+* Implement <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> or use the default implementation
+* Register the service in the DI container
+* The validation system automatically uses the registered service to format validation error responses
+
+The following example shows how to register and configure the <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> to customize validation error responses:
+
+:::code language="csharp" source="~/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/Program.cs" id="snippet_register_IProblemDetailsService_implementation" :::
+
+When a validation error occurs, the <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> will be used to generate the error response, including any customizations added in the `CustomizeProblemDetails` callback.
+
+For a complete app example, see the [Minimal API sample app](https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/minimal-apis/10.0-samples/MinApiIproblemDetailsService/Program.cs) demonstrating how to customize validation error responses using the <xref:Microsoft.AspNetCore.Http.IProblemDetailsService> in ASP.NET Core Minimal APIs.
+
 #### Text
 
 :::code language="csharp" source="~/fundamentals/minimal-apis/9.0-samples/Snippets/Program.cs" id="snippet_08":::