Linq to SQL: add a custom column and the Order By it

SELECT *, ISNULL(DueDate, DATEADD(year, 10, GETDATE())) AS DueDateForSorting
FROM Tasks
ORDER BY DueDateForSorting

SELECT * FROM Tasks
ORDER BY ISNULL(DueDate, DATEADD(year, 10, GETDATE()))

from o in dc.Orders orderby o.DueDate ?? DateTime.Today.AddYears(10)

[Column(Storage="_DueDate", DbType="SmallDateTime")]
public System.Nullable<System.DateTime> DueDate
{
    get
    {
    	if(this._DueDate == null)
    	{
    		return DateTime.Today.AddYears(10);
    	}
    	return this._DueDate;
    }