Unable to catch the Dropdown selected value in a textbox inside a repeater
<p>I have a <code>DropDownList</code> inside a repeater and whenever the selected text is changed, I have to show it in a <code>TextBox</code> but I'm getting <code>Object reference not set to an instance of an object</code> error</p>

<pre><code>protected void Ddl_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ddl   = (DropDownList)  sender;
    RepeaterItem item  = (RepeaterItem)  ddl .NamingContainer;
    TextBox txt        = (TextBox) item.FindControl("TextBox4");
    txt.Text           = ddl.SelectedItem.Text;
}
</code></pre>
