Fix case of DefaultValue using enum backing type.

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectPropertyDescriptor.cs

@@ -300,7 +300,7 @@ private object DefaultValue
                         object? defaultValue = ((DefaultValueAttribute)a).Value;
                         bool storedAsUnderlyingType = defaultValue != null && PropertyType.IsEnum && PropertyType.GetEnumUnderlyingType() == defaultValue.GetType();
                         _defaultValue = storedAsUnderlyingType ?
-                            Enum.ToObject(PropertyType, _defaultValue!) :
+                            Enum.ToObject(PropertyType, defaultValue!) :
                             defaultValue;
                     }
                     else

src/libraries/System.ComponentModel.TypeConverter/tests/DescriptorTestComponent.cs

@@ -5,6 +5,12 @@
 
 namespace System.ComponentModel.Tests
 {
+    internal enum DescriptorTestEnum
+    {
+        Value0 = 0,
+        Value1 = 1
+    }
+
     internal class DescriptorTestComponent : IComponent, ISite
     {
         private Dictionary<Type, object> _services;
@@ -17,6 +23,9 @@ internal class DescriptorTestComponent : IComponent, ISite
         [DefaultValue(DefaultPropertyValue)]
         public int Property { get; set; }
 
+        [DefaultValue(0)]
+        public DescriptorTestEnum EnumProperty { get; set; }
+
         public object PropertyWhichThrows { get { throw new NotImplementedException(); } }
 
         public string StringProperty { get; private set; }

src/libraries/System.ComponentModel.TypeConverter/tests/PropertyDescriptorTests.cs

@@ -144,6 +144,17 @@ public void ShouldSerializeValueReturnsTrueWhenValueIsNotDefault()
             Assert.True(propertyDescriptor.ShouldSerializeValue(component));
         }
 
+        [Fact]
+        public void ShouldSerializeValueHandlesEnumWithBackingTypeDefaultValue()
+        {
+            var component = new DescriptorTestComponent();
+            component.EnumProperty = DescriptorTestEnum.Value1;
+            var properties = TypeDescriptor.GetProperties(component.GetType());
+            PropertyDescriptor propertyDescriptor = properties.Find(nameof(component.EnumProperty), false);
+
+            Assert.True(propertyDescriptor.ShouldSerializeValue(component));
+        }
+
         [Fact]
         public static void ReadOnlyPropertyReturnsTrue()
         {