ASP.NET 下拉列表必填字段驗證器不起作用

Question

將必填字段驗證器添加到下拉列表時，它不會使其成為必填項。

這是代碼：

<td style="height: 14px">Parent</td>
<td style="height: 14px">
    <asp:DropDownList ID="ddlParentReportingCat" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlParentReportingCat_SelectedIndexChanged" CausesValidation="True"></asp:DropDownList>
    <asp:RequiredFieldValidator ID="rfvParentReportingCat" runat="server" InitialValue="0" ControlToValidate="ddlParentReportingCat" ErrorMessage="*" Display="Dynamic" ></asp:RequiredFieldValidator>
</td>

這是后面的代碼：

protected void ddlParentReportingCat_SelectedIndexChanged(object sender, EventArgs e)
{
    var parentReportingCategoryId = ddlParentReportingCat.SelectedValue.ParseInt32();
    
    if (parentReportingCategoryId.IsNotNullOrZero())
    {
        ddlChildReportingCat.DataSource = reportingCategoryAdministrator.GetByParent(parentReportingCategoryId);
        ddlChildReportingCat.DataTextField = "ReportingCategoryName";
        ddlChildReportingCat.DataValueField = "Id";
        ddlChildReportingCat.DataBind();
    }

    if (parentReportingCategoryId.IsNullOrZero())
    {
        return;
    }

    PageFunction.SetDdlValue(ddlChildReportingCat, ProductClass.ReportingCategoryId.ToString());
    SetEnabledStateOfDdlTaxCode();
    SetProductFormData();
    SetMiniWizardLinksData();
}

public static void BindParentReportingCatDDL(DropDownList ddl)
{
    BindDDL(ddl, "ReportingCategory", "ReportingCategoryID",
            "SELECT ReportingCategoryID, ReportingCategory FROM dbo.tblReportingCategory WHERE (ParentReportingCategoryID IS NULL) ORDER BY ReportingCategory");
}

列表中的數據來自數據庫。

Answer 1

設置 InitialValue="-1" 並讓它工作！ 謝謝！