c# - RadComboBox 选择的值错误

Question

当我使用RadComboBox时，我遇到以下问题:

    ddl_contactList.Items.Clear();
    ddl_contactList.DataSource = ContactList.GetContactListsByDep(year, main_code);
    ddl_contactList.DataTextField = "list_desc";
    ddl_contactList.DataValueField = "list_code";
    ddl_contactList.DataBind();
    ddl_contactList.Items.Insert(0, new Telerik.Web.UI.RadComboBoxItem("NewList", "-1"));
    ddl_contactList.SelectedIndex = 0;

---

  <telerik:RadComboBox ID="ddl_contactList" runat="server" AutoPostBack="True" CausesValidation="False"
            CollapseDelay="0" Culture="ar-EG" ExpandDelay="0" Filter="StartsWith" ItemsPerRequest="10"
            MarkFirstMatch="true" Skin="Outlook" EnableAutomaticLoadOnDemand="True" EmptyMessage="-List name-"
            ShowMoreResultsBox="True" 
            onselectedindexchanged="ddl_contactList_SelectedIndexChanged" AppendDataBoundItems ="true">
    </telerik:RadComboBox>

---

组合框中的项目数始终为1!!!尽管数据源包含许多项目，所以当我尝试随时获取任何项目的选定值时，我总是得到 -1 !!

如何获取正确的selectedvalue？

Answer 1

在数据绑定(bind)之前添加 NewList 项，并将以下属性添加到 RadComboBox。

将 AppendDataBoundItems 设置为 True 会保留 RadComboBox 中已存在的项目。这使您可以将 RadComboBox 绑定(bind)到多个数据源或使用未绑定(bind)和绑定(bind)模式。

然后将数据源添加到控件。

ddl_contactList.Items.Clear();
ddl_contactList.Items.Insert(0, new Telerik.Web.UI.RadComboBoxItem("NewList", "-1"));
ddl_contactList.SelectedIndex = 0;


ddl_contactList.DataSource = ContactList.GetContactListsByDep(year, main_code);
ddl_contactList.DataTextField = "list_desc";
ddl_contactList.DataValueField = "list_code";
ddl_contactList.DataBind();