Razor

                                
                                        
string columnTemplate = "case when strftime('%m', OrderDate) = '{month}' then (Invoices.UnitPrice*Quantity) end as period{month}";
string fromPart = "Invoices join Products on Products.ProductID = Invoices.ProductId";

var columns = new List() { "CategoryId" };
var labels = new List() {"Category"};

for (int month = 1; month <= 12; month++)
{
    columns.Add(columnTemplate.Replace("{month}", month.ToString("00")));
    labels.Add(CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(month));
}

DbNetGridCore productSalesByCategoryGrid = new DbNetGridCore("northwind", fromPart);
productSalesByCategoryGrid.Columns = columns;
productSalesByCategoryGrid.Labels = labels;
productSalesByCategoryGrid.GroupBy = true;

for (int month = 1; month <= 12; month++)
{
    productSalesByCategoryGrid.Column($"period{month.ToString("00")}").Format("c").DataType(typeof(Decimal)).Aggregate(AggregateType.Sum);
}

productSalesByCategoryGrid.Column("CategoryId").Lookup(new Lookup("Categories", "CategoryId", "CategoryName"));
@productSalesByCategoryGrid.Render()