LINQ - Add property to results

Add it with partial classes:

public partial class Courses
{
    public String NewProperty { get; set; }
}

Then you can assign it after you've created the object.

I suppose you could return a new object composed of the new property and the selected object, like this:

var query = from x in db.Courses
                select new
                {
                    Course = x,
                    NewProperty = true
                };