using System;
  using System.Windows;
  using System.Windows.Controls;
  using System.Windows.Input;
  using System.Windows.Markup;
  
  namespace RoboforkApp
  {
      public class ToolboxItem : ContentControl
      {
          private Point? dragStartPoint = null;
  
          static ToolboxItem()
          {
              FrameworkElement.DefaultStyleKeyProperty.OverrideMetadata(typeof(ToolboxItem), new FrameworkPropertyMetadata(typeof(ToolboxItem)));
          }
  
          protected override void OnPreviewMouseDown(MouseButtonEventArgs e)
          {
              base.OnPreviewMouseDown(e);
              this.dragStartPoint = new Point?(e.GetPosition(this));
          }
  
          protected override void OnMouseMove(MouseEventArgs e)
          {
              base.OnMouseMove(e);
              if (e.LeftButton != MouseButtonState.Pressed)
              {
                  this.dragStartPoint = null;
              }
  
              if (this.dragStartPoint.HasValue)
              {
                  Point position = e.GetPosition(this);
                  if ((SystemParameters.MinimumHorizontalDragDistance <=
                      Math.Abs((double)(position.X - this.dragStartPoint.Value.X))) ||
                      (SystemParameters.MinimumVerticalDragDistance <=
                      Math.Abs((double)(position.Y - this.dragStartPoint.Value.Y))))
                  {
                      string xamlString = XamlWriter.Save(this.Content);
                      DataObject dataObject = new DataObject("DESIGNER_ITEM", xamlString);
  
                      if (dataObject != null)
                      {
                          DragDrop.DoDragDrop(this, dataObject, DragDropEffects.Copy);
                      }
                  }
  
                  e.Handled = true;
              }
          }
      }
  }