I want to sort when user click colums, but there is error when it clicked. (see attach: Error01.png)

I write the code by http://www.intersoftsolutions.com/Support/WebGrid/Tutorial/Text/Create-WebGrid-in-Server-Side-programmatically/

There is not struncture of root table in webgrid.

only the code like:

<ISWebGrid:WebGrid>
<LayoutSettings RowHeightDefault="26px" AllowSorting="Yes">
...
</LayoutSettings>
</ISWebGrid:WebGrid>

 How can I fix it?