Private Sub YourControl_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles YourControl.MouseDown
    e.Handled = True
End Sub

private void  MouseDown(object sender, MouseButtonEventArgs e)
      {
          e.Handled = true;
          if (e.LeftButton == MouseButtonState.Pressed)
         {
            this.DragMove();
          }

          if (e.LeftButton == MouseButtonState.Released)
          {
          //your mouse up code
          }
      }