[Solved] Cannot Resove Symbol 'Custom' - Custom Button

[Jamie]

I am trying to add a custom button but am getting stuck - and getting the error

Cannot Resolve Symbol 'Custom'

here's my "Columns" block

.Columns(columns =>
        {
            columns.Command(commands =>
            {
                commands.Edit().ButtonType(GridButtonType.Image);
                commands.Delete().ButtonType(GridButtonType.Image);
            }).Width(65);
            
            columns.Command(commands => commands
                    .Custom("viewDetails")                    // Error here.......
                    .Text("Customer Details")
                    .DataRouteValues(route => route.Add(o => o.OrderID).RouteKey("orderID"))
                    .Ajax(true)
                    .Action("ViewDetails", "Grid"))
                .HtmlAttributes(new { style = "text-align: center" })
                .Width(150);
            
            columns.Bound(o => o.DocName).Width(172);
            columns.Bound(o => o.DocDescription).Width(130);
            columns.Bound(o => o.aspnet_Users.UserName).Width(130).Title("Owner");
        })

I am following this example - so what am I doing wrong?
http://demos.telerik.com/aspnet-mvc/razor/grid/customcolumncommand

[Jamie]

Whoops - never mind - I had a reference to an old dll in my project

false alarm! :)