Group By multiple Columns in DataTable using LINQ in C# and VB.Net

I am not asking like that . This is my datatable 

DataTable dt = GetDataTableFromExcel();
List<DataTable> dts = dt.AsEnumerable()
                .GroupBy(row => row.Field<string>("OUTLET NAME "))
                .Select(g => g.CopyToDataTable()).ToList();

As it is selecting based on Outlet name, here i want to select based another column too using C# with Linq query. I tried like this but not working.

DataTable dt = GetDataTableFromExcel();
List<DataTable> dts = dt.AsEnumerable()
                .GroupBy(row => row.Field<string>("OUTLET NAME ","Occasion"))
                .Select(g => g.CopyToDataTable()).ToList();