如何在asp.net的列表框中获取所选值

Question

 foreach (ListItem item in ListBoxMembers.Items)
 {
     if (item.Selected)
     {
         countSelected += 1;
     }

 }   
 for (int counter = 0; counter < countSelected; counter++)
 {
    string firstName = ListBoxMembers.SelectedItems[counter].Value;
 }

这不会返回选定的值.我哪里错了？它抛出的错误是System.Web.UI.WebControls不包含listboxmembers.selectedItems错误的defenition

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using MySql.Data.MySqlClient;
using MySql.Data;
using System.Web.Security;
using System.Data;
using System.Web.UI.WebControls;

这些是我正在使用的名称空间.

这就是我想要做的

 for (int counter = 0; counter < countSelected; counter++)
            {

        //To get User ID
            string firstName=ListBoxMembers.SelectedItems[counter].Value;

           // string firstName = ListBoxMembers.Items[counter].Value;
            string GUserIDQueryText = "SELECT UserID FROM tbl_user WHERE FirstName ";
            int userID = Convert.ToInt32(server.performQuery(GUserIDQueryText, firstName, MySqlDbType.VarChar));

            //Insert into tbl_userGroups
            string insertIDText = "INSERT INTO tbl_usergroups 

(tbl_group_GroupID,tbl_user_UserID) VALUES(@tbl_group_GroupID,@tbl_user_UserID)";
...
     }

我想将所有选定的用户添加到表中.

它抛出的错误是System.Web.UI.WebControls不包含listboxmembers.selectedItems的defenition你是否缺少目录或程序集指令.为什么我无法使用selectedItems

Answer 1

countSelected  =  ListBoxMembers.Items.Cast<ListItem>().Where(i => i.Selected).Count();

如果你想要获得所有选定的项目,你可以这样做

var selectedNames = ListBoxMembers.Items.Cast<ListItem>()
                                  .Where(i => i.Selected)
                                  .Select(i => i.Value)
                                  .ToList()