Question

我的Web表单页面上有一个用户定义的类型下拉列表（DDL），它继承自System.Web.UI.WebControls.DropDownList。我在页面的代码文件（.aspx.cs）和AppCode中填写我的DDL而不会出现错误。

public static void FillDropDownList(ListControl drp)
{
    drp.Items.Clear();
    drp.Items.Add(new ListItem("Please select", ""));
    drp.Items.Add(new ListItem("False", false.ToString()));
    drp.Items.Add(new ListItem("True", true.ToString()));
}

然后我正在初始化我的DDL：

drp.SelectedValue = "False";

初始化在页面的代码文件（aspx.cs）中的填充方法时有效。在AppCode中的Fill方法初始化不起作用，我收到以下错误。

Cannot have multiple items selected in a DropDownList. Please send a copy of this message to the Support. 

at System.Web.UI.WebControls.DropDownList.VerifyMultiSelect() 
at System.Web.UI.WebControls.ListControl.RenderContents(HtmlTextWriter writer) 
at System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.Control.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) 
at System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at ASP.fleetnetnew_masterpages_fleetpopuppage_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\fleetintlpdvl\204737b8\cd934b62\App_Web_jw12vu5i.2.cs:line 0 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.Control.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
at System.Web.UI.Page.Render(HtmlTextWriter writer) 
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

我需要使用AppCode来填充DDL，这样我就可以从中心点填充我的DDL。我在这里缺少什么？

Answer 1

1）在aspx页面中添加下拉列表（使用AppendDataBoundItems）

<asp:DropDownList runat="server" ID="drpTest" AppendDataBoundItems="true" />

2）在页面后面的c＃代码中

    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            FillDropDownList(drpTest);

            // select False after filling drop down list
            drpTest.Items.FindByValue("False").Selected = true;
        }

        public static void FillDropDownList(ListControl drp)
        {
            drp.Items.Clear();
            drp.Items.Add(new ListItem("Please select", ""));
            drp.Items.Add(new ListItem("False", false.ToString()));
            drp.Items.Add(new ListItem("True", true.ToString()));
        }
    }

＆＃34;不能在下拉列表中选择多个项目＆＃34; AppCode出错

1 个答案: