Specified cast is not valid in lambda expression of DataRow List while fetching a column value

Question

I've a DataTable orders and I'm using lambda expression to filter out the records without any loops. The first line in the if condition works fine and returns me a valid record.

if (orders.Rows.Count > 0)
{
    //This line returns a record
    var defaultOrder = orders.Rows.Cast<DataRow>().Where(p => p.Field<bool>("IsDefault")).ToList();
    //The line below gives me an exception  Specified cast is not valid.
    var defaultOrderID = orders.Rows.Cast<DataRow>().Where(p => p.Field<bool>("IsDefault")).Select(p => p.Field<long>("OrderID")).FirstOrDefault();
}

Now, I want to fetch value of a specific column from this record but I'm getting following exception

PS: I can see in DB and defaultOrder variable in debug mode that value of OrderID is 4 . Datatype of IsDefault is bit and OrderID is int in Database. Both are not null .

Answer 1

if OrderID is Type of int

replace

p.Field<long>("OrderID")

with

 p.Field<int>("OrderID")

Answer 2

You can check the data type of the field "OrderID" in DataRow, Rows will have no. of records under it, Expand any 1 record, Column properties, Select the field "OrderID" and check the data type of it.

If it is giving error for long and it has value 4 in DB than it should have a data type of Int32, use that one.

var defaultOrderID = orders.Rows.Cast<DataRow>().Where(p => p.Field<bool>("IsDefault")).Select(p => p.Field<Int32>("OrderID")).FirstOrDefault();