1. 首先繼承一個listbox，來獲得按住ctrl鍵時，點選的item

  public class ListBoxEx : ListBox
   {
      public BeatTemplateWave GetAnitem()
        {           
            var obj = this.AnchorItem;
            if (obj != null)
            {
                Type type = obj.GetType();
                System.Reflection.PropertyInfo propertyInfo = type.GetProperty("Item", BindingFlags.Instance | BindingFlags.NonPublic);
                System.Reflection.PropertyInfo propertyInfo2 = type.GetProperty("Index", BindingFlags.Instance| BindingFlags.NonPublic);
                BeatTemplateWave value_Old = (BeatTemplateWave)propertyInfo.GetValue(obj, null); //獲取屬性值
                return value_Old;
            }
            else
            {
                return null;
            }
        }

//重寫選中
public void Setlist(List<BeatTemplateWave> list)
{
this.SetSelectedItems(list);
}

   }

2 在listbox 的呼叫處： 獲得listbox 的選中項：SelectedItemsList

3 在mouseleftdown事件裡面新增處理程式

   private void MouseLeftButtonUpHandler(ElementMouseButtonEventMerge embem)
        {
           
            ListBoxEx listbox = (embem.Sender as ListBoxEx);
            if (Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl))
            {
                List<BeatTemplateWave> selectlist = new List<BeatTemplateWave>();
                var obj = (embem.Sender as ListBoxNoWheelEx).GetAnitem();
                if (SelectedItemsList != null)
                {
                    var templist = SelectedItemsList.IListToCollection<BeatTemplateWave>();
                    if (obj != null)
                    {
                        //判斷滑鼠點選的項在不在選中的裡面，如果不在，則加入臨時集合，如果在選中項裡面，則不加入臨時集合，
 
 
                        if (templist.Any(p => p.R == obj.R))
                        {
                            foreach (BeatTemplateWave a in templist)
                            {
                                if (a.R == obj.R)
                                {
                                }
                                else
                                {
                                    selectlist.Add(a);
                                }
                            }
                        }
                        else
                        {
                            selectlist.Add(obj);
                            selectlist.AddRange(templist);
                        }
                    }
                    else
                    {
                        selectlist.AddRange(templist);
                    }
                    listbox.Setlist(selectlist);    //重新選中              
                    SelectedItemsList = selectlist;//將臨時集合賦值給選中項 重寫選中
 

                }
                return;
            }
            else
            {
                if (listbox.SelectedItems != null)
                {
                    SelectedItemsList = listbox.SelectedItems;
                    var item = SelectedItemsList;
                    if (item.Count == 0)
                        return;
                   
                }
            }
         
        }