我有一个ASP.NET页面有两个输入元素：
> ReadOnly的TextBox.此TextBox是CalendarExtender的TargetControl
>具有AutoPostBack = True的DropDownList
这是代码：
<table border="0" cellpadding="0" cellspacing="0">
<tr><td colspan="2">Date:</td></tr>
<tr><td colspan="2">
<asp:TextBox ID="dateTextBox" runat="server" ReadOnly="true" />
<ajax:CalendarExtender ID="datePicker" runat="server" Format="MM/dd/yyyy" OnLoad="datePicker_Load" TargetControlID="dateTextBox" />
</td></tr>
<tr><td colspan="2">Select an Option:</td></tr>
<tr>
<td>Name: </td>
<td><asp:DropDownList ID="optionsDropDownList" runat="server" AutoPostBack="true"
OnLoad="optionsDropDownList_Load"
OnSelectedIndexChanged="optionsDropDownList_SelectedIndexChanged"
DataTextField="Name" DataValueField="ID" />
</td></tr>
<tr><td><asp:Button ID="saveButton" runat="server" Text="Save" OnClick="saveButton_Click" /></td></tr>
</table>
当DropDownList发回时,用户使用datePicker选择的日期将重置为当前日期.另外,如果我查看dateTextBox的Text属性,它等于string.Empty.
如何保留用户在PostBack上选择的日期？
