List Box : help preventing duplicate items

13 Nov 2006 8:15 PM

arkgroup

Hi,

Is there any way I can prevent adding same value to the list box?
Do I have to loop thru list every time I add item?
For instance, I can add 1/1/2006 as value and text many times
And I try to avoid this.

Thanks

13 Nov 2006 8:34 PM

MikeS

You can check if an item exists without looping.

    Private Sub AddItem(ByVal s As String, ByVal lb As ListBox)
        Dim li As New ListItem(s)
        If lb.Items.Contains(li) = False Then
            lb.Items.Add(li)
        End If
    End Sub

13 Nov 2006 9:00 PM

arkgroup

Mike,
I am using C# and code below did not work for some reason...
(lst is my ListBox)

private bool IsDuplicate(string value)
    {

        ListItem li = new ListItem(value);
        if (lst.Items.Contains(li))
            return true;

return false;
}

MikeS wrote:
Show quoteHide quote

> You can check if an item exists without looping.
>
>     Private Sub AddItem(ByVal s As String, ByVal lb As ListBox)
>         Dim li As New ListItem(s)
>         If lb.Items.Contains(li) = False Then
>             lb.Items.Add(li)
>         End If
>     End Sub

13 Nov 2006 10:28 PM

MikeS

C# ?

Oh, I see now, that came on my DVD too, nifty.

This seems to work, even though it gives cramps to type.

....Using *.*...;
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        for (int i = 0; i < 10; i++)
        {
            for (int j = 0; j < 10; j++)
            {
                String s = (i + j).ToString();
                if (!isDuplicate(s))
                    ListBox1.Items.Add(s);
            }
        }
    }
    private bool isDuplicate(String s)
    {
        ListItem li = new ListItem(s);
        return ListBox1.Items.Contains(li);
    }
}

14 Nov 2006 3:26 PM

arkgroup

Mike,

Your code did not produce any duplicates and isDuplicate always return
false.
Here what is working for me:

private bool IsDuplicate(string value)
    {

        ListItem li = ListBox1.Items.FindByValue(value);
        return ListBox1.Items.Contains(li);

}

Thanks for your time.

MikeS wrote:
Show quoteHide quote

> C# ?
>
> Oh, I see now, that came on my DVD too, nifty.
>
> This seems to work, even though it gives cramps to type.
>
> ...Using *.*...;
> public partial class _Default : System.Web.UI.Page
> {
>     protected void Page_Load(object sender, EventArgs e)
>     {
>         for (int i = 0; i < 10; i++)
>         {
>             for (int j = 0; j < 10; j++)
>             {
>                 String s = (i + j).ToString();
>                 if (!isDuplicate(s))
>                     ListBox1.Items.Add(s);
>             }
>         }
>     }
>     private bool isDuplicate(String s)
>     {
>         ListItem li = new ListItem(s);
>         return ListBox1.Items.Contains(li);
>     }
> }

14 Nov 2006 5:03 PM

MikeS

The code produces duplicates here.

If I make this comment:

//if (!isDuplicate(s))

The list fills with all kinds of dupes.

Glad you got it working anyway.