Infragistics v15.2 webdatagrid - Unable to find control in Template column

Question

Recently I have upgraded my app from infragistics v12.2 to 15.2

I am using 'TemplateDataField' of webdatagrid in many places.

After upgrading to 15.2, my controls & pages were unable to find controls of Template column

foreach (GridRecord row in grd1.Rows)
{
        WebNumericEditor txtqty = ((WebNumericEditor)row.Items.FindItemByKey("Quantity").FindControl("txtActualQty"));
        if (Convert.ToInt32(txtqty.Value) <= 0)
}

in above code, I am unable to find 'txtqty' is null.

 <ig:TemplateDataField Key="Quantity" Header-Text="RT Exp">
     <ItemTemplate>
         <cc1:WebNumericEditor ID="txtActualQty" runat="server" CssClass="textbox" 
              onblur="return validateQuantity(this)" Width="90%" MaxLength="11" 
              Value='<%# DataBinder.Eval(((Infragistics.Web.UI.TemplateContainer)Container).DataItem, "Quantity")  %>'>
         </cc1:WebNumericEditor>
     </ItemTemplate>
 </ig:TemplateDataField>