Mvvm combobox绑定Dictionary问题

常规绑定方式：

ViewModel层：  public Dictionary<string, string>MathRelationCollection{ get; set; }//属性

//赋值                          

MathRelationCollection = new Dictionary<string, string>();
MathRelationCollection = DynamicQueryHelper.GetMathCollection();

UI 绑定：ItemsSource="{Binding LogicRelationCollecion}" DisplayMemberPath="{Binding Key, Mode=OneWay}" SelectedValuePath="{Binding Value, Mode=OneWay}"

问题：前台Combobox显示为：[key,value]

解决方法：ItemsSource="{Binding LogicRelationCollecion}" DisplayMemberPath=“Key" SelectedValuePath="Value"

虽然解决了，但为什么会这样，还没想到，也欢迎大家多多提示