C# 如何将DropDownList SelectedItem传递到EntityDataSource Select属性

我正在尝试将ddlCity DROPDOLLIST的选定值传递到EntityDataSource2 CommandText，其中“where p.city=@city”，但出现以下错误：

除非指定了AutoGenerateWhere==true或Where，否则无法指定Where参数

城市
找不到。。。

如果您有任何帮助，我们将不胜感激

<asp:EntityDataSource
....
    <WhereParameters>
        <asp:ControlParameter ControlID="costLimit" DbType="Int32" 
          DefaultValue="2500" Name="ordercost" PropertyName="SelectedValue"
        ConvertEmptyStringToNull="true" />
      </WhereParameters>
.....
</asp:EntityDataSource>

---

这是在EntityDataSource的Select属性中传递dropdownlist selectedvalue的正确版本

    <tr id="SearchDropDown">     
    <asp:EntityDataSource ID="EntityDataSource1" runat="server" 
    ConnectionString="name=medicaldb2Entities" 
    DefaultContainerName="medicaldb2Entities" EnableFlattening="False" 
    EntitySetName="Medicals" Select="it.[medicalName], it.[city], it.[Region]">
</asp:EntityDataSource>    
<td>
<td>
<asp:DropDownList ID="ddlCity" runat="server" AutoPostBack="true"
onselectedindexchanged="ddlCity_SelectedIndexChanged"
    DataSourceID="EntityDataSource1" DataTextField="city" 
    DataValueField="city">
</asp:DropDownList>
</td>
</tr>
</table>



<asp:ListView ID="ListView1" runat="server" DataSourceID="EntityDataSource2">

<LayoutTemplate>
            <table>
                <tr>
                    <td>
                        City
                    </td>

                </tr>
                <asp:PlaceHolder ID="ItemPlaceHolder" runat="server"></asp:PlaceHolder>
            </table>
        </LayoutTemplate>
        <ItemTemplate>
            <tr>
                <td>
                    <%# Eval("city") %>
                </td>
            </tr>
        </ItemTemplate>

        <EmptyDataTemplate>
            not found...
        </EmptyDataTemplate>

</asp:ListView>

 <asp:EntityDataSource ID="EntityDataSource2" runat="server" 
 ConnectionString="name=medicaldb2Entities" 
    DefaultContainerName="medicaldb2Entities" 
EntitySetName="Medicals" 
   Select= "it.[MedicalID], it.[medicalName], it.[city], it.[Region], it.[description], it.[Image], it.[adress]"
    Where = "it.[city] = @city">

    <WhereParameters> 
    <asp:ControlParameter ControlID="ddlCity" DbType="String" 
      DefaultValue="2500" Name="city" PropertyName="SelectedValue"
    ConvertEmptyStringToNull="true" />
  </WhereParameters>

</asp:EntityDataSource>


城市
找不到。。。
我已经试过了，我把它改为ControlID=“ddlCity”和Name=“City”。然后我再次将查询写为p.city=@city，但它不起作用。我假设您的代码中存在语法错误。您可以阅读Msdn中的语法或发布您的代码。我将一些属性添加到参数中。一旦您向我展示了正确的方法，我会将您的答案标记为正确，但我在下面发布的完整版本您可以查看本教程。我相信你会得到你的答案。谢谢，这看起来像是一个有用的教程，我必须阅读它
    <tr id="SearchDropDown">     
    <asp:EntityDataSource ID="EntityDataSource1" runat="server" 
    ConnectionString="name=medicaldb2Entities" 
    DefaultContainerName="medicaldb2Entities" EnableFlattening="False" 
    EntitySetName="Medicals" Select="it.[medicalName], it.[city], it.[Region]">
</asp:EntityDataSource>    
<td>
<td>
<asp:DropDownList ID="ddlCity" runat="server" AutoPostBack="true"
onselectedindexchanged="ddlCity_SelectedIndexChanged"
    DataSourceID="EntityDataSource1" DataTextField="city" 
    DataValueField="city">
</asp:DropDownList>
</td>
</tr>
</table>



<asp:ListView ID="ListView1" runat="server" DataSourceID="EntityDataSource2">

<LayoutTemplate>
            <table>
                <tr>
                    <td>
                        City
                    </td>

                </tr>
                <asp:PlaceHolder ID="ItemPlaceHolder" runat="server"></asp:PlaceHolder>
            </table>
        </LayoutTemplate>
        <ItemTemplate>
            <tr>
                <td>
                    <%# Eval("city") %>
                </td>
            </tr>
        </ItemTemplate>

        <EmptyDataTemplate>
            not found...
        </EmptyDataTemplate>

</asp:ListView>

 <asp:EntityDataSource ID="EntityDataSource2" runat="server" 
 ConnectionString="name=medicaldb2Entities" 
    DefaultContainerName="medicaldb2Entities" 
EntitySetName="Medicals" 
   Select= "it.[MedicalID], it.[medicalName], it.[city], it.[Region], it.[description], it.[Image], it.[adress]"
    Where = "it.[city] = @city">

    <WhereParameters> 
    <asp:ControlParameter ControlID="ddlCity" DbType="String" 
      DefaultValue="2500" Name="city" PropertyName="SelectedValue"
    ConvertEmptyStringToNull="true" />
  </WhereParameters>

</asp:EntityDataSource>