multiple selection on listbox

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My sample code:

C#

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)

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]

Posted 16-Nov-12 19:09pm

Member 8172875

Updated 17-Nov-12 1:57am

Nelek

v2

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sahabiswarup · Accepted Answer · 2012-11-16T19:44:00

C#

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
                }
            }
        }

Do you want this?
or

C#

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;
}

and for all records

C#

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();
        }

Dominic Abraham · Accepted Answer · 2012-11-17T02:54:00

Solution 2

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:

C#

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];
 }

Posted 17-Nov-12 2:54am

Dominic Abraham

Updated 18-Nov-12 20:11pm

v4

Comments

Dominic Abraham 18-Nov-12 1:29am

If the solution is helpful, please mark it as answer.

Member 8172875 18-Nov-12 23:38pm

Error 1: The best overloaded method match for 'string.Join(string, string[])' has some invalid arguments

Error 2: Argument '2': cannot convert from 'System.Collections.Generic.List<string>' to 'string[]'

I got two errors while trying your code.. you are correct. i am working on windows application.

Dominic Abraham 19-Nov-12 1:40am

can you try after adding the namespace System.Collections.Generic also if not done. I checked this only in .Net 4.0. And you may be checking in old .Net version.

Dominic Abraham 19-Nov-12 2:11am

Please check the improved solution.

Member 8172875 19-Nov-12 2:15am

thanks Dominic. i have done with some modification on your code and its working properly .. thanks for the help

Member 8172875 19-Nov-12 2:17am

int itemCount = listBox1.SelectedItems.Count;
string str="";

for (int i = 0; i < itemCount; i++)
{

str += listBox1.SelectedItems[i].ToString() + "','";

}

Dominic Abraham 19-Nov-12 3:21am

Good...Whenever the post is helpful, don't forget to mark it as answer. Then it will be helpful to others also.