Debugger shows property as field (#35433)

src/ExpressionEvaluator/CSharp/Test/ResultProvider/ExpansionTests.cs

@@ -629,6 +629,40 @@ class C
                 EvalResult("F", "1", "object {int}", "(new C()).s1.F"));
         }
 
+        [Fact]
+        public void NullableProperty()
+        {
+            var source =
+@"
+class R
+{
+    public int? A { get; set; }
+    public int? B { get; set; }
+}
+class C
+{
+    R r = new R();
+    public C()
+    {
+        r.A = 1;
+        r.B = null;
+    }
+}";
+            var assembly = GetAssembly(source);
+            var type = assembly.GetType("C");
+            var value = CreateDkmClrValue(Activator.CreateInstance(type));
+            var rootExpr = "new C()";
+            var evalResult = FormatResult(rootExpr, value);
+            Verify(evalResult,
+                EvalResult(rootExpr, "{C}", "C", rootExpr, DkmEvaluationResultFlags.Expandable));
+            var children = GetChildren(evalResult);
+            Verify(children,
+                EvalResult("r", "{R}", "R", "(new C()).r", flags: DkmEvaluationResultFlags.Expandable));
+            Verify(GetChildren(children[0]),
+                EvalResult("A", "1", "int?", "(new C()).r.A", category: DkmEvaluationResultCategory.Property),
+                EvalResult("B", "null", "int?", "(new C()).r.B", category: DkmEvaluationResultCategory.Property));
+        }
+
         [Fact]
         public void Pointers()
         {

src/ExpressionEvaluator/Core/Source/ResultProvider/ResultProvider.cs

@@ -459,6 +459,8 @@ private void CreateEvaluationResultAndContinue(EvalResult result, WorkList workL
                 // which typically appears to be set to the default value ("Other").
                 var category = (result.Category != DkmEvaluationResultCategory.Other) ? result.Category : value.Category;
 
+                var nullableMemberInfo = value.GetDataItem<NullableMemberInfo>();
+
                 // Valid value
                 return DkmSuccessEvaluationResult.Create(
                     InspectionContext: inspectionContext,
@@ -469,10 +471,10 @@ private void CreateEvaluationResultAndContinue(EvalResult result, WorkList workL
                     Value: display,
                     EditableValue: result.EditableValue,
                     Type: typeName,
-                    Category: category,
-                    Access: value.Access,
-                    StorageType: value.StorageType,
-                    TypeModifierFlags: value.TypeModifierFlags,
+                    Category: nullableMemberInfo?.Category ?? category,
+                    Access: nullableMemberInfo?.Access ?? value.Access,
+                    StorageType: nullableMemberInfo?.StorageType ?? value.StorageType,
+                    TypeModifierFlags: nullableMemberInfo?.TypeModifierFlags ?? value.TypeModifierFlags,
                     Address: value.Address,
                     CustomUIVisualizers: customUIVisualizers,
                     ExternalModules: null,
@@ -557,6 +559,16 @@ private void CreateEvaluationResultAndContinue(EvalResult result, WorkList workL
                 }
                 else
                 {
+                    // nullableValue is taken from an internal field.
+                    // It may have different category, access, etc comparing the original member.
+                    // For example, the orignal member can be a property not a field.
+                    // Save original member values to restore them later.
+                    if (value != nullableValue)
+                    {
+                        var nullableMemberInfo = new NullableMemberInfo(value.Category, value.Access, value.StorageType, value.TypeModifierFlags);
+                        nullableValue.SetDataItem(DkmDataCreationDisposition.CreateAlways, nullableMemberInfo);
+                    }
+
                     value = nullableValue;
                     Debug.Assert(lmrNullableTypeArg.Equals(value.Type.GetLmrType())); // If this is not the case, add a test for includeRuntimeTypeIfNecessary.
                     // CONSIDER: The DynamicAttribute for the type argument should just be Skip(1) of the original flag array.
@@ -1058,5 +1070,21 @@ private void Execute()
                 _state = State.Executed;
             }
         }
+
+        private class NullableMemberInfo : DkmDataItem
+        {
+            public readonly DkmEvaluationResultCategory Category;
+            public readonly DkmEvaluationResultAccessType Access;
+            public readonly DkmEvaluationResultStorageType StorageType;
+            public readonly DkmEvaluationResultTypeModifierFlags TypeModifierFlags;
+
+            public NullableMemberInfo(DkmEvaluationResultCategory category, DkmEvaluationResultAccessType access, DkmEvaluationResultStorageType storageType, DkmEvaluationResultTypeModifierFlags typeModifierFlags)
+            {
+                Category = category;
+                Access = access;
+                StorageType = storageType;
+                TypeModifierFlags = typeModifierFlags;
+            }
+        }
     }
 }