Asp.net:ScriptManager 不工作

Question

我正在尝试从另一个下拉列表填充一个下拉列表(过滤数据)我知道我想制作一个脚本管理器，但它给了我一个错误:

The control with ID '' requires a ScriptManager on the page. The ScriptManager must appear before any controls that need it.

这是我的代码:

 <td>School</td>
     <td>
         <asp:ScriptManager ID="ScriptManager1" runat="server" />
         <asp:DropDownList ID="SchoolRegister" runat="server" AutoPostBack="True" 
             DataSourceID="SqlDataSource1" DataTextField="SchoolName" DataValueField="ID">
         </asp:DropDownList>
         <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
             ConnectionString="<%$ ConnectionStrings:DanielConnectionString %>" 
             SelectCommand="SELECT * FROM [Schools]"></asp:SqlDataSource>
     </td>
 </tr>
 <tr>
     <td>Class</td>
     <td>
         <asp:ScriptManager ID="ScriptManager2" runat="server" />
         <asp:DropDownList ID="ClassRegister" runat="server" 
             DataSourceID="SqlDataSource2" DataTextField="ClassName" DataValueField="ID">
         </asp:DropDownList>
         <asp:SqlDataSource ID="SqlDataSource2" runat="server" 
             ConnectionString="<%$ ConnectionStrings:DanielConnectionString %>" 
             SelectCommand="SELECT * FROM [Class] WHERE ([SchoolID] = @SchoolID)">
             <SelectParameters>
                 <asp:ControlParameter ControlID="SchoolRegister" Name="SchoolID" 
                     PropertyName="SelectedValue" Type="Int32" />
             </SelectParameters>
         </asp:SqlDataSource>
     </td>
 </tr>

谢谢。

Answer 1

您的页面上有多个 ScriptManager 控件。你只需要一个，它应该放在页面顶部附近。