var query = from customerRow in db.CustomerTable
            from orderRow in db.OrderTable
            where customerRow.CustomerID == orderRow.CustomerID
            select new
            {
                customerRow.CustomerID,
                orderRow.OrderID
            };

SELECT [t0].[CustomerID], [t1].[OrderID]
FROM [dbo].[tblCustomer] AS [t0], [dbo].[tblOrder] AS [t1]
WHERE [t0].[CustomerID] = [t1].[CustomerID]

SELECT tblCustomer.[CustomerID], tblOrder.[OrderID]
FROM tblCustomer
INNER JOIN tblOrder ON tblCustomer.[CustomerID] = tblOrder.[OrderID]