Can't access the control in a listview
<p>Can't access the control in a listview</p>

<p><strong>error</strong></p>

<p>Object reference not set to an instance of an object.</p>

<p><strong>.cs</strong></p>

<pre><code>public void lnkaddtocart_Command(Object sender, CommandEventArgs e)
{
  ((TextBox)ListView_ProductDetails.FindControl("txtbox_pqty")).Visible = false;   
}
</code></pre>

<p><strong>.aspx</strong></p>

<pre><code>&lt;asp:ListView runat="server" ID="ListView_ProductDetails"&gt;
     &lt;LayoutTemplate&gt;
        &lt;asp:PlaceHolder ID="itemPlaceholder" runat="server"&gt;&lt;/asp:PlaceHolder&gt;
     &lt;/LayoutTemplate&gt;
     &lt;ItemTemplate&gt;
              &lt;div class="qty"&gt;
                  Qty:
                  &lt;asp:TextBox ID="txtbox_pqty" Text="1" runat="server"/&gt;
                  &lt;input type="hidden" name="product_id" size="2" value="41" /&gt;
                       &lt;asp:LinkButton ID="lnkaddtocart" runat="server" 
                            CommandArgument='&lt;%#Eval("pid") %&gt;' 
                            OnCommand="lnkaddtocart_Command"  
                            cssclass="button"&gt;
                               &lt;span&gt;Add to Cart&lt;/span&gt;
                        &lt;/asp:LinkButton&gt;
                  &lt;/div&gt;
    &lt;/ItemTemplate&gt;
&lt;/asp:ListView&gt;
</code></pre>
