从一个DropDownList asp.net获得价值选择 [英] Get selected value from a dropdownlist asp.net

问题描述

我知道这是一个愚蠢的问题，但我不能找出如何从我的dropdownlist获得选择的值：（

I know this is a silly question but i can't find out how to get the selected value from my dropdownlist :(

初​​始化DropDownList的：

Init the dropdownlist:

             SqlCommand command = new SqlCommand("SelectAllUserID", connection);
             command.CommandType = CommandType.StoredProcedure;

            SqlDataReader sqlReader = command.ExecuteReader();
            if (sqlReader.HasRows)
            {
                TProjectMID.DataSource = sqlReader;
                TProjectMID.DataTextField = "UserID";
                TProjectMID.DataValueField = "UserID";
                TProjectMID.DataBind();
            }

尝试获取的下拉列表中选择值：

Try to get the value of drop down list:

                String a;
                a = TProjectMID.SelectedValue;
                a = TProjectMID.SelectedItem.Value;
                a = TProjectMID.DataValueField;
                a = TProjectMID.Text;

它没有回我选择的价值，它使返回默认值时，才出现DropDownList的？

It didn't return the value I chose, it keeps returning the default value when the dropdownlist appear ??

谁能告诉我我做错了什么？谢谢

Can anybody tell me what I did wrong ? Thank you

推荐答案

您需要确保你没有重新加载DDL每次页面加载，换句话说，不仅填补它的初始页面加载，如果它在一个页面回发，不要再加载它，因此值将被保留。

You need to make sure you are not re-loading the DDL everytime the page loads, in other words only fill it on the initial page load, and if it is a page postback, don't re-load it so the value will be retained.

这样的事情应该工作：

   protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack) {

         SqlCommand command = new SqlCommand("SelectAllUserID", connection);
         command.CommandType = CommandType.StoredProcedure;

          SqlDataReader sqlReader = command.ExecuteReader();
          if (sqlReader.HasRows)
          {
            TProjectMID.DataSource = sqlReader;
            TProjectMID.DataTextField = "UserID";
            TProjectMID.DataValueField = "UserID";
            TProjectMID.DataBind();
          }
        }

}

，然后在code检索值，这应该工作：

and then in your code to retrieve the value, this should work:

   string a = TProjectMID.SelectedValue;

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