修复WPF Silverlight ListBox控件的一个Bug

先来看这样演示程序。在修复前，选择重复的数字会导致选中状态混乱，出现多个数字莫名其妙被选中的状况。

刨根问题，此问题最终定位到如下代码(WPF 项目，Silverlight项目类似)：

/*
internal bool Select(object o, bool assumeInItemsCollection);
  
Declaring Type: System.Windows.Controls.Primitives.Selector+SelectionChanger 
Assembly: PresentationFramework, Version=4.0.0.0 
*/
internal bool Select(object o, bool assumeInItemsCollection)
{
    if (!Selector.ItemGetIsSelectable(o)) return false;
    if (!assumeInItemsCollection && !this._owner.Items.Contains(o))
    {
        if (!this._toDeferSelect.Contains(o)) this._toDeferSelect.Add(o);
        return false;
    }
    if (!this._toUnselect.Remove(o))
    {
        if (this._owner._selectedItems.Contains(o)) return false;
        if (this._toSelect.Contains(o)) return false;
        if (!this._owner.CanSelectMultiple && this._toSelect.Count > 0)
        {
            foreach (object obj2 in (IEnumerable) this._toSelect)
            {
                this._owner.ItemSetIsSelected(obj2, false);
            }
            this._toSelect.Clear();
        }
        this._toSelect.Add(o);
    }
    return true;
}

由于使用的是Items.Contains(o)判断，所以会导致值类型的重复数据判断出错。当然修复此问题的思想就是把值类型转换为引用类型。

创建如下代码

public class WrapObject<T>
{
    private T _obj;
 
    public WrapObject(T o)
    {
        _obj = o;
    }
 
    public static implicit operator WrapObject<T>(T o)
    {
        return new WrapObject<T>(o);
    }
 
    public static explicit operator T(WrapObject<T> o)
    {
        return o._obj;
    }
 
    public T UnWrap()
    {
        return _obj;
    }
 
    public override string ToString()
    {
        return _obj == null ? null : _obj.ToString();
    }
}