Displaymember path not working in my custom control in WPF

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C#

WPF

WinRT

My custom control is deriving from itemscontrol but it will not work.when use below code works fine.

public new string DisplayMemberPath
       {
         get { return (string)GetValue(DisplayMemberPathProperty); }
          set { SetValue(DisplayMemberPathProperty, value); }
       }

       ///// <summary>
       ///// Using a DependencyProperty as the backing store for SearchItemPath.  This enables animation, styling, binding, etc...
       ///// </summary>
       public static readonly new DependencyProperty DisplayMemberPathProperty =
        DependencyProperty.Register("DisplayMemberPath", typeof(string), typeof(SfRadialMenu), new PropertyMetadata(null));

What I have tried:

can you please explain the reason