How to avoid duplicate items being added from one CheckBoxList to another CheckBoxList
<p>While adding items from one <code>CheckBoxList</code> to another <code>CheckBoxList</code> how to check if the item is already present in the second <code>CheckBoxList</code> using asp.net c#</p>

<p>The code I have written to move between <code>CheckBoxLists</code> is:</p>

<pre><code>protected void add_Click(object sender, EventArgs e)
    {
        for (int i = 0; i &lt;= CheckBoxList2.Items.Count - 1; i++)
        {
            if (CheckBoxList2.Items[i].Selected)
            {
                CheckBoxList3.Items.Add(CheckBoxList2.Items[i]);
                CheckBoxList3.ClearSelection();
            }
        }
    }
</code></pre>

<p>I am using <strong>add_Click</strong> button to move items between lists.
I need to validate while adding items.</p>

<p>Kindly help. Thank you..!!</p>
