2 group by in different classes in linq code example

Example 1: linq group by multiple

.GroupBy(x => new { x.Column1, x.Column2 })

Example 2: Group by linq multiple columns C#

var query = (from t in Transactions
             group t by new {t.MaterialID, t.ProductID}
             into grp
                    select new
                    {
                        grp.Key.MaterialID,
                        grp.Key.ProductID,
                        Quantity = grp.Sum(t => t.Quantity)
                    }).ToList();