unable to use class from the server in the client

I am trying to register server class so that I will be able to call a function in the server from the client using ajax.
In the page load function in the server I wrote:
Public class Cls
Protected Sub Page_Load1(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Ajax.Utility.RegisterTypeForAjax(GetType(cls))
End sub
End class

I have a function which I want to call from the client:
<Ajax.AjaxMethod(HttpSessionStateRequirement.ReadWrite)> _
Public Function IsOKToDeleteCategory(ByVal rowIndex As Integer) As Boolean
End function

In the client I have a java script funtion where I am trying to call to the function IsOKToDeleteCategory:
function canDeleteCategory()
{
Cls. IsOKToDeleteCategory(3);
}

When I run the page I get an error saying that the the Cls class is undefined in the client side

The client-side cannot call a server-side function, but it can call a script on the server-side with variables. That server-side script can then call that function.