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Checking the list

how to check if an item is selected in my list? so I have a delete button, but I want this button to only execute if an item is selected in the list. im using asp.net code behind c #. I would prefer this check to be done server side.

amuses ..

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6 answers 


for (int i = 0; i < lbSrc.Items.Count; i++)
{
    if (lbSrc.Items[i].Selected == true)
    {
        lbSrc.Items.RemoveAt(lbSrc.SelectedIndex);
    }
}


here's what i came up with.

-1


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In the callback, click the button, just check if the selected index in the list box is greater or equal to zero.



protected void removeButton_Click( object sender, EventArgs e )
{
    if (listBox.SelectedIndex >= 0)
    {
        listBox.Items.RemoveAt( listBox.SelectedIndex );
    }
}
+1


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Actually the SelectedIndex is zero based, so your check should be:

if (listBox.SelectedIndex> = 0) ...

+1


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To remove multiple elements, you need to parse the elements in reverse order.

protected void removeButton_Click(object sender, EventArgs e)
{
    for (int i = listBox.Items.Count - 1; i >= 0; i--)
        listBox.Items.RemoveAt(i);
}

If you disassemble it as usual, the result will be quite unexpected. Example: If you delete item 0, then item 1 becomes the new item 0. If you now try to delete what you think is item 1, you are effectively deleting what you see as item 2.

+1


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You might want to go with an early breakout based on your problem and that ListBox.SelectedIndex will return -1 if nothing is selected .

to borrow some tvanfosson event handler code.

protected void removeButton_Click( object sender, EventArgs e )
{
    if (listBox.SelectedIndex < 0) { return; }
    // do whatever you wish to here to remove the list item 
}
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To remove an item from the collection, you need to loop back.

for (int i=lbSrc.Items.Count - 1, i>=0, i--)
{
   //code to check the selected state and remove the item
}
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