add partial codes

src/Shared/HandyControl_Shared/Tools/Extension/CustomAttributeExtension.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Reflection;
+
+namespace HandyControl.Tools.Extension
+{
+    internal static class CustomAttributeExtension
+    {
+        public static Attribute GetCustomAttribute(this MemberInfo element, Type attributeType) => Attribute.GetCustomAttribute(element, attributeType);
+
+        public static T GetCustomAttribute<T>(this MemberInfo element) where T : Attribute => (T)GetCustomAttribute(element, typeof(T));
+    }
+}