Question

I am using WCf service in my windowsApplication… I got the exception in my client When i am trying to add items in Listbox by using ForEach Loop… The exception is “Collection was modified enumuration may not execute”.
How shall i solve this exception….

And my code is,

            foreach (ClsPC pc in iclsobj.GetPC())
            {
            if (listBox1.Items.Count == 0)
            {
            listBox1.Items.Add(pc.IPAddress);
             }
            else
            {
            for (int i = 0; i < listBox1.Items.Count; i++)
            {
            if (!listBox1.Items[i].ToString().Contains(pc.IPAddress))
            {
            listBox1.Items.Add(pc.IPAddress);
             }
          }
        }
       }
 client.Close();

client = null;

}

Answer 1

You’re trying to modify the collection in you list box while looping through it (the inner loop), which isn’t really such a hot idea. You’d be better performing this in your data select (i.e. a get distinct PC), or limiting the returned list, possibly something like:

var pcs = iclsobj.GetPC().Select(pc => new { IPAddress = pc.IPAddress}).Distinct();

And then just binding your listbox to this.