dropdownlist选择的值使我感到困惑吗? [英] dropdownlist selected value confused me?

问题描述

嘿
从下拉列表中选择组时，我有asp.net页面下拉列表和按钮
然后单击按钮，然后按钮通过查询字符串发送所选值(组ID)
然后根据查询字符串中的ID进行页面浏览组详细信息，这是第一次发生
但是当我从下拉列表更改组时，查询字符串仍然具有最后一个ID
和我的代码

hey
i have asp.net page dropdownlist and button when choose my group from dropdownlist
and click button then button send selected value (group-id) via query string
then page view group detail based on id in query string this happens the first time
but when i change group from dropdownlist the query string still has the last id
and my code

protected void Page_Load(object sender, EventArgs e)
    {
       

        if (!IsPostBack) FillList();

        if (Request.QueryString["id"] != null)
        {
            
           
                FillData();
                div_General.Visible = true;
                div_Special.Visible = true;
                dropdownlist1 .SelectedValue = Request.QueryString["id"];

        }
    }

    protected void button1_Click(object sender, EventArgs e)
    {
        if (dropdownlist1 .SelectedIndex== 0)
        {
            par_ErrorMessage.InnerText = "choose group first  ...";
            par_ErrorMessage.Visible = true;
        }
        else Response.Redirect("Authority.aspx?id=" + dropdownlist1.SelectedValue);
    }

当我单击按钮并假设
中的新值时，我想到了这个问题 dropdownlist页面生命周期首先转到页面加载，并且在此代码中

i figured the problem in this when i click button and suppose that new value in
dropdownlist page life cycle go to page load first and in this code

dropdownlist1 .SelectedValue = Request.QueryString["id"];

从button1_click
读取之前，将所选值返回到最后一个值 请帮助我

return selected value to the last one before read it from button1_click
plz i need help

推荐答案

您可以为页面加载事件后的下拉列表选择值

You can Select Value for Drop Down after Page Load Event

protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack) 
      {
        FillList();
        Viewstate["id"] = Request.QueryString["id"];
         if (Request.QueryString["id"] != null)
           {
            FillData();
            div_General.Visible = true;
            div_Special.Visible = true;

           }
      }
}

现在，在Page_PreRender中，您可以在下拉菜单中选择值"，如下所示:-

Now in Page_PreRender you can Select Value in dropdown like this:-

protected void Page_PreRender(object sender, EventArgs e)
{
  if(!Page.IsPostBack)
 {
   if (ViewState["id"] != null)
      {
          dropdownlist1 .SelectedValue = ViewState["id"].ToString();
       }
  }
}

通过Rahul om stackoverflow

via Rahul om stackoverflow

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