Can not find a control using the FindControl on RowCreated for Gridview

Question

I am using a gridview, and here is one of my templatefields:

<asp:TemplateField HeaderText="Quantity" SortExpression="Quantity">
    <HeaderTemplate>
        <asp:Label ToolTip="Quantity" runat="server" Text="Qty"></asp:Label>
    </HeaderTemplate>
    <EditItemTemplate>
        <asp:TextBox ID="txt_Quantity" runat="server" Text='<%# Bind("Quantity") %>' Width="30px"
            Enabled='True'></asp:TextBox>
    </EditItemTemplate>
</asp:TemplateField>

I am tring to reach txt_Quantity like this

    protected void begv_OrderDetail_RowCreated(object sender, GridViewRowEventArgs e)
    {
        TextBox txt_Quantity = (TextBox)e.Row.FindControl("txt_Quantity");
        txt_Quantity.Attributes.Add("onFocus", "test(this)");
    }

This is the error message:

System.NullReferenceException: Object reference not set to an instance of an object.

Answer 1

RowCreated is executed for every RowType(btw, the same as with RowDataBound), so for the header, data-row, footer or pager.

The first row is the header-row, but the TextBox is in rows with RowType=DataRow. Since it's in the EditItemTemplate you also have to check the EditIndex:

protected void begv_OrderDetail_RowCreated(object sender, GridViewRowEventArgs e)
{
    if (row.RowType == DataControlRowType.DataRow
       && e.Row.RowIndex == begv_OrderDetail.EditIndex)
    {
        TextBox txt_Quantity = (TextBox)e.Row.FindControl("txt_Quantity");
        txt_Quantity.Attributes.Add("onFocus", "test(this)");
    }
}

Note that if you enumerate the Rows property of the GridView you only get the rows with RowType=DataRow, so the header, footer and pager are omitted. So here no additional check is needed:

foreach(GridViewRow row in begv_OrderDetail.Rows)
{
    // only DataRows
}