下拉列表在回发时失去价值 [英] dropdownlist losing value on postback

问题描述

我在Gridview中使用自定义分页。我已经创建了一个Control，其中有一个下拉列表来选择页面大小。一切正常，但当我刷新页面时，下拉列表丢失了它的价值

这里是我的代码

I am using Custom paging in Gridview. I have created a Control in which there is a dropdown to selece page size. Everything works fine but when i am refreshing page the dropdown lost it's value
here is my code

<asp:DropDownList ID="ddlPageRowSize" EnableViewState="True" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlPageRowSize_SelectedIndexChanged">
                <asp:ListItem Value="10">10</asp:ListItem>
                <asp:ListItem Value="20">20</asp:ListItem>
                <asp:ListItem Value="50">50</asp:ListItem>
                <asp:ListItem Value="100">100</asp:ListItem>
            </asp:DropDownList>

页面加载我保存下拉列表选择值在viewstate这里是我的代码

on page load i am saving dropdown selected value in viewstate here is my code

protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack) return;
        ViewState["PageSize"] = ddlPageRowSize.SelectedItem.Value;
    }
// suppose i have selected 100 from dropdown and then refresh the page 
// ddlPageRowSize.SelectedItem.Value always returns 10 

我做错了什么可以有人建议....

what wrong i am doing can anyone suggest....

推荐答案

你的页面加载事件应该是这样的事情

your page load event should be soemthing like this

protected void Page_Load(object sender, EventArgs e)
    {

  //  if (!Page.IsPostBack)
  //  {
     //do something
   // }
   // else
   // {
     //   ddlPageRowSize.SelectedIndex= Convert.ToInt32(Session["index"]);

         if(Session["index"] == null)
         {
             //do something
         }
         else
         {
             ddlPageRowSize.SelectedIndex= Convert.ToInt32(Session["index"]);  
         }


    }

您在ddlPageRowSize_SelectedIndexChanged事件中将值设置为会话，例如

where you set the value to the session in the ddlPageRowSize_SelectedIndexChanged event like

protected void ddlPageRowSize_SelectedIndexChanged(object sender, EventArgs e)
{
    Session["index"] = ddlPageRowSize.SelectedIndex;
}

已选择=True到您的列表项目将解决您的问题。

Selected="True" to your list item will solve your problem.

<asp:DropDownList ID="ddlPageRowSize" EnableViewState="True" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlPageRowSize_SelectedIndexChanged">
                <asp:ListItem Selected="True" Value="10">10</asp:ListItem>
                <asp:ListItem Value="20">20</asp:ListItem>
                <asp:ListItem Value="50">50</asp:ListItem>
                <asp:ListItem Value="100">100</asp:ListItem>
            </asp:DropDownList>

请使用以下代码。

please use the following code.

protected void Page_Load(object sender, EventArgs e)
{

    if (Session["PageSize"] != null)
        ddlPageRowSize.SelectedValue = Convert.ToString(Session["PageSize"]);

}

protected void ddlPageRowSize_SelectedIndexChanged(object sender, EventArgs e)
{
    Session["PageSize"] = ddlPageRowSize.SelectedValue;
}

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