From c0e2100cd29f458b22883153d48ec84b31f40c8f Mon Sep 17 00:00:00 2001
From: Oleh Puzakov <opuzakov@gmail.com>
Date: Tue, 22 Jul 2025 16:00:50 +0200
Subject: [PATCH] Fix RequestDelegateFactory to handle nullable types correctly
 in empty request body scenarios

---
 .../src/RequestDelegateFactory.cs             |  4 +++-
 .../test/RequestDelegateFactoryTests.cs       | 21 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/Http/Http.Extensions/src/RequestDelegateFactory.cs b/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
index 19965ef1fc31..70f9b4b08f7a 100644
--- a/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
+++ b/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
@@ -1375,7 +1375,9 @@ private static Expression AddResponseWritingToMethodCall(Expression methodCall,
         {
             object? defaultBodyValue = null;
 
-            if (allowEmptyRequestBody && bodyType.IsValueType)
+            var isNullableType = bodyType.IsGenericType && bodyType.GetGenericTypeDefinition() == typeof(Nullable<>);
+
+            if (allowEmptyRequestBody && bodyType.IsValueType && !isNullableType) // Nullable types should be left null
             {
                 defaultBodyValue = CreateValueType(bodyType);
             }
diff --git a/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs b/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
index 083da9bd7aed..35fb8c9ddd47 100644
--- a/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
+++ b/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
@@ -896,6 +896,27 @@ public async Task RequestDelegateRejectsEmptyBodyGivenExplicitFromBodyParameter(
         Assert.Equal(400, httpContext.Response.StatusCode);
     }
 
+    [Fact]
+    public async Task RequestDelegatePopulatesNullFromBodyNullableParameterWithEmptyBody()
+    {
+        var httpContext = CreateHttpContext();
+        httpContext.Request.Headers["Content-Type"] = "application/json";
+        httpContext.Request.Headers["Content-Length"] = "0";
+        httpContext.Features.Set<IHttpRequestBodyDetectionFeature>(new RequestBodyDetectionFeature(false));
+
+        var factoryResult = RequestDelegateFactory.Create(
+            ([FromBody] int? body) =>
+            {
+                httpContext.Items["body"] = body;
+            }
+        );
+
+        var requestDelegate = factoryResult.RequestDelegate;
+        await requestDelegate(httpContext);
+
+        Assert.Null(httpContext.Items["body"]);
+    }
+
     [Fact]
     public void RequestDelegateFactoryThrowsForByRefReturnTypes()
     {