列表框上的多项选择 [英] multiple selection on listbox

问题描述

我的示例代码:

My sample code:

string str = "";
 
foreach(ListItem lstIetm In MyListBox.Items)// through an exception here "unable to cast object of type 'System.String' to 'System.Web.UI.WebControls.ListItem'" 

{ 
  If(lstIetm.Selected) 
  { 
    str+=lstItem.Value.ToString()+","; 
  } 
} 
if(str!="") 
{ 
    str.Remove(str.LastIndexOf(',')); 
} 
 
Select * from <tablename> where Id in (str)

请建议我如何解决此异常及其发生的原因.我遍历所有资源.但是我有相同的foreach循环.

[edit]添加了代码块[/edit]

please suggest me how to resolve this exception and why it occurs. i go through all the resources. but i got the same foreach loop.

[edit]code block added[/edit]

推荐答案

if (ListBox1.Items.Count > 0)
        {
            for (int i = 0; i < ListBox1.Items.Count; i++)
            {
                if (ListBox1.Items[i].Selected)
                {
                    string selectedItem = ListBox1.Items[i].Text;
                    //insert command
                }
            }
        }

你要这个吗?
或

Do you want this?
or

public string GetListBoxSelStringInComma(ListBox Listbox1)
{
string selectedItem = "";
if (Listbox1.Items.Count > 0)
{
for (int i = 0; i < Listbox1.Items.Count; i++)
{
if (Listbox1.Items[i].Selected)
{
if (selectedItem == "")
selectedItem = Listbox1.Items[i].Text;
else
selectedItem += "," + Listbox1.Items[i].Text;
}
}
}
return selectedItem;
}

和所有记录

and for all records

protected void btnSelectAll_Click(object sender, EventArgs e)
        {
            int _count = lstEmployees.Items.Count;
            if (_count != 0)
            {
                for (int i = 0; i < _count; i++)
                {
                    ListItem item = new ListItem();
                    item.Text = lstEmployees.Items[i].Text;
                    item.Value = lstEmployees.Items[i].Value;
                    lstSelectedEmployees.Items.Add(item);
                }
            }
            lstEmployees.Items.Clear();
        }

嗨
我认为您尝试使用"Selected"属性选择的上述代码适用于Web应用程序，而您尝试使用Windows应用程序.

您可以尝试以下代码:

Hi
I think the above code you tried with "Selected" property is for web application and you are trying with windows application.

Can you try the below code:

using System.Collections.Generic;

int itemCount = listBox1.SelectedItems.Count;
List<string> lstItems = new List<string>();

for (int i = 0; i < itemCount; i++)
{
    lstItems.Add(listBox1.SelectedItems[i].ToString());
}
//string myInQuery = string.Join(",",lstItems);
 string myInQuery = string.Empty;
 for (int i = 0; i < lstItems.Count; i++)
 {
    if (myInQuery != string.Empty)
    {
        myInQuery = string.Format("{0},{1}",myInQuery, lstItems[i]);
    }
    else
       myInQuery = lstItems[i];
 }

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