silverlight combobox 在使用 ItemsSource 之前，项集合必须为空

<pre name="code" class="csharp">/// <summary>
        /// 初始化ComboBox
        /// </summary>
        void InitialComboBox() 
        {
            List<NameValueModel> listKaiDao = EnumHelper.GetEnumsList(typeof(KaiDaoEnum));
            listKaiDao.Insert(0,new NameValueModel("",null));
            cmboKaiDao.ItemsSource = listKaiDao;
            cmboKaiDao.displayMemberPath = "Name";
            cmboKaiDao.SelectedValuePath = "Value";
            cmboKaiDao.Selectedindex = 0;

            List<NameValueModel> listShuaiGua = EnumHelper.GetEnumsList(typeof(dispatchActionEnum));
            //listShuaiGua.Insert(0,null));
            cmboShuaiGua.ItemsSource = listShuaiGua;
            cmboShuaiGua.displayMemberPath = "Name";
            cmboShuaiGua.SelectedValuePath = "Value";
            cmboShuaiGua.Selectedindex = 0;
        }

comboBox 报错，在使用 ItemsSource 之前，项集合必须为空,后来定睛一看，原来是我在前台xaml中也写了集合项，

<pre name="code" class="html"><ComboBox x:Name="cmboKaiDao" Width="50" Style="{StaticResource comboBoxStyle}">
                    <ComboBoxItem>开</ComboBoxItem>
                    <ComboBoxItem>到</ComboBoxItem>
                </ComboBox>

改为

<pre name="code" class="html"><ComboBox x:Name="cmboKaiDao" Width="50" Style="{StaticResource comboBoxStyle}">
                </ComboBox>

ok，问题解决