在轉發器控件中獲取選定的下拉列表值

Question

我有一個轉發器控件內的dropdownlist，我正在嘗試獲取值，並且我得到“對象引用未設置為對象的實例”。 我不知道還有什么可以嘗試的。 謝謝

ASPX代碼：

   <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>

代碼背后：

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.
    }                   
}

我在保存所選值時遇到問題..

Answer 1

我在代碼中找到的是你循環遍歷generalrepeater項目。 您正在以dataItem的身份訪問轉發器項。 我在這里嘗試了這個代碼，理想情況下你的代碼應該說

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

代替

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