How do I sublass a control along with its attached properties?

I am trying to subclass System.Windows.Contro开发者_开发百科ls.DataGrid in order to add special commands to which a view model can bind. How do I do this and still have the Columns attached property? Do I have to declare it against my new type in order to use it?

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Columns is not an attached property.. you should use it the same way you always do, just replace DataGrid with your-control-name:

<my:MyDataGrid>
  <my:MyDataGrid.Columns>
     <!--  Columns goes here --->
  </my:MyDataGrid.Columns>
</my:MyDataGrid>