Double is not a nullable type [closed]

Question

I am doing this with LINQ:

        // let use Linq
        var DateMarket = from p in Orders_From_CRD.AsEnumerable()
                         where p.Field<Double>("Fill_ID") != null
                         select OrderTable.Rows.Add(p.Field<DateTime>("trade_date"), p.Field<string>("ticker"),
                         p.Field<Double>("EXEC_QTY"), p.Field<Double>("EXEC_PRICE"));

        TradeTable = DateMarket.CopyToDataTable();

But I have an error telling me

Cannot cast DBNull.Value to type 'System.Double'. Please use a nullable type.

Do you know how to cast nullable type in this case ?

I tried <Double?> and I got 'Specified cast is not valid.'

Answer 1

You could use:

p.Field<Double?>

T? is shorthand for Nullable<T>, a wrapper for a value type that allows null values.

Answer 2

Use the type :

Double?  

when you need a nullable double

Answer 3

by default, double can't be assigned null values. The solution to this problem is to use a nullable type : Double?

try this:

        var DateMarket = from p in Orders_From_CRD.AsEnumerable()
                     where p.Field<Double?>("Fill_ID") != null
                     select OrderTable.Rows.Add(p.Field<DateTime>("trade_date"), p.Field<string>("ticker"),
                     p.Field<Double?>("EXEC_QTY"), p.Field<Double?>("EXEC_PRICE"));

    TradeTable = DateMarket.CopyToDataTable();