c# - SelectedValue 无效，因为它不存在于项目列表中

Question

这是我得到的错误:

ddlRankEdit' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

我有一个带有多个下拉列表的表单，这些下拉列表嵌套在默认设置为不可见的面板中。当用户从单独的列表框中选择记录时，所选索引更改事件将面板设置为可见并进行数据调用。那是错误发生的时候。看下面的代码，我在停顿的地方添加了 XXX。

<asp:DropDownList runat="server" ID="ddlRankEdit" CssClass="txtfield" DataSourceID="ODCRanks"
  DataTextField="Rank" DataValueField="ID" AppendDataBoundItems="True">
  <asp:ListItem Text="--- Select a Rank ---" Value="-1" />                                            
  </asp:DropDownList>
  <asp:ObjectDataSource ID="ODCRanks" runat="server" 
    OldValuesParameterFormatString="original_{0}" SelectMethod="GetRanks" 
    TypeName="RanksTableAdapters.RankTableAdapter"></asp:ObjectDataSource>

protected void lboxManageMembers_SelectedIndexChanged(object sender, EventArgs e)
{
    pnlReviewMemberDetails.Visible = false;
    pnlUnlockUserAccount.Visible = false;
    pnlAdmins.Visible = false;
    pnlCreateAdmins.Visible = false;
    lblNote.Visible = false;
    pnlManageMenbers.Visible = true;

    MembershipUser user = Membership.GetUser();
    DataSetTableAdapters.MemberInfoTableAdapter da = new DataSetTableAdapters.MemberInfoTableAdapter();

    Guid _memberId = Guid.Empty;
    _memberId = new Guid(lbxManageMembers.SelectedValue);
    DataSet.MemberInfoDataTable dt = da.GetMember(_memberId);
    if (dt.Rows.Count == 1)
    {
        DataSet.MemberInfoRow mr = dt[0];

   XXX ddlRankEdit.SelectedValue = Convert.ToString(mr.rankid);
   XXX ddlPatrolEdit.SelectedValue = Convert.ToString(mr.patrolid);
   XXX ddlPositionEdit.SelectedValue = Convert.ToString(mr.bsaposid);

        txtFirstNameEdit.Text = mr.firstname;
        txtLastNameEdit.Text = mr.lastname;
        txtEmailEdit.Text = user.Email;
        txtAddressEdit.Text = mr.address;
        txtPhoneEdit.Text = mr.phone;
        txtCellPhoneEdit.Text = mr.altphone;
        txtAltEmailEdit.Text = mr.altemail;

        txtMotherFirstNameEdit.Text = mr.parentfn;
        txtMotherLastNameEdit.Text = mr.parentln;
        txtMotherWorkPhoneEdit.Text = mr.parentworkphone;
        txtMotheHomePhoneEdit.Text = mr.parentworkphone;
        txtMotherCellkPhoneEdit.Text = mr.parentscellphone;
        txtMotherTwitterEdit.Text = mr.parenttwitter;
        txtMotherEmailEdit.Text = mr.parentemail;
        txtMotherAltEmailEdit.Text = mr.parentemailalt;

        txtFatherFirstNameEdit.Text = mr.parent2fn;
        txtFatherLastNameEdit.Text = mr.parent2ln;
        txtFatherWorkPhoneEdit.Text = mr.parent2workphone;
        txtFatherHomePhoneEdit.Text = mr.parent2workphone;
        txtFatherCellPhoneEdit.Text = mr.parent2cellphone;
        txtFatherTwitterEdit.Text = mr.parent2twitter;
        txtFatherEmailEdit.Text = mr.parent2email;
        txtFatherAltEmailEdit.Text = mr.parent2emailalt;
    }

}

Answer 1

错误消息准确地告诉您发生了什么:例如存储在 mr.rankid 中的值不在下拉列表中。

您需要确定下拉列表是否包含正确的值，或者您尝试分配的值是否不存在于可用值列表中。

更新

由于似乎是包含面板的可见性导致了问题，因此最好使用 CSS 隐藏面板而不是将 Visible 属性设置为 false，这将阻止它渲染到页面。

这可以在代码隐藏中使用类似于以下的代码来完成:

Panel1.Style.Add(HtmlTextWriterStyle.Visibility, "Hidden");
Panel1.Style.Add(HtmlTextWriterStyle.Display, "None");