C# 在中继器控件内获取选定的dropdownlist值

我在一个中继器控件中有dropdownlist，我试图获取该控件的值，并且得到“对象引用未设置为对象的实例”。我不知道还能尝试什么。谢谢

ASPX代码：

   <asp:Repeater ID="GeneralRepeater" runat="server" 
             OnItemDataBound="GeneralRepeater_OnItemDataBound" 
                onitemcommand="GeneralRepeater_ItemCommand">
            <HeaderTemplate></HeaderTemplate>
            <ItemTemplate>
            <tr>
             <td class="style2">
             </td>
              <td class="style2">
                 <asp:DropDownList ID="GeneralDDL"  AppendDataBoundItems="true"  DataTextField="DiagnosisCode" 
                  DataValueField="DiagnosisCode" runat="server" AutoPostBack="True" />
               </td>

            </tr>
            </ItemTemplate>
            <FooterTemplate></FooterTemplate>
            </asp:Repeater>
        </asp:Panel>

protected void GeneralRepeater_OnItemDataBound(object sender,
                                               RepeaterItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item ||
            e.Item.ItemType == ListItemType.AlternatingItem)
        {
            DropDownList myDDL = (DropDownList)e.Item.FindControl("GeneralDDL");
            Diagnosis oDiagnosis = new Diagnosis();
            DataView dv = new DataView(oDiagnosis.GetDiagnosis());
            myDDL.DataSource = dv;
            myDDL.DataTextField = "DiagnosisCode";
            myDDL.DataValueField = "DiagnosisCode";
            myDDL.DataBind();

        }
    }

protected void cmdSave_Click(object sender, EventArgs e)
{
    string ProductSelected;
    string FeatureSelected;
    string SectionSelected;


    foreach(RepeaterItem dataItem in GeneralRepeater.Items)
    {
         ProductSelected = ((DropDownList)GeneralRepeater.FindControl("GeneralDDL")).SelectedItem.Text; //error Object reference not set to an instance of an object.
    }                   
}

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我在保存所选值时遇到问题。

我在代码中发现，您正在遍历generalrepeater项。您正在以dataItem访问中继器项。我在这里试用了这个代码，理想情况下，您的代码应该是

foreach(RepeaterItem dataItem in GeneralRepeater.Items)        
{               
  ProductSelected = ((DropDownList)dataItem.FindControl("GeneralDDL")).SelectedItem.Text; //No error
}

而不是

foreach(RepeaterItem dataItem in GeneralRepeater.Items) 
{
   ProductSelected = ((DropDownList)GeneralRepeater.FindControl("GeneralDDL")).SelectedItem.Text; //error Object reference not set to an instance of an object.
} 

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我还没试过，但我认为绿色环保是对的。虽然“数据项”可能有点用词不当。