Linq - Add Row to results for display only

Question

I have a linq query that returns a brief order summary - product description and product price that gets bound to a data control. I want to add a row to be bound in this same control that displays tax information. The product description column would simply say "Tax" and the product price column would give a tax amount.

I used to retrieve a DataTable of these results and simply do a NewRow() and then set the datasource of my control as the DataTable. I'm looking for the equivalent technique when using LINQ to SQL. Thanks.

Answer 1

In order to make it easy to add another "row" to the results of the LINQ query, you might want to consider creating a class to hold the results of the query. Then you could convert the results to a List, calculate the tax, and append the tax as an object of the class.

public class OrderSummary
{
    public string Description { get; set; }
    public decimal Amount { get; set; }
}


var taxRate = ...
var orderSummary = db.Orders.Where( o => o.ID == id )
                            .Select( o => new OrderSummary
                                {
                                    Description = o.Product
                                                   .Details
                                                   .Description,
                                    Amount = o.Qty * o.Product.Price
                                })
                            .ToList();

var tax = new OrderSummary
              {
                  Description = "Tax",
                  Amount = orderSummary.Sum( o => o.Amount * taxRate );
              };
orderSummary.Add( tax );

Then you can bind the list to your control using Description as the key and Amount as the value.

Answer 2

orderSummary.Union(taxRow)