LINQ error: “<object> has no parameterless constructor.”

Question

I have a class method GetMS() as defined below, but when the method is called I get an error stating \'SLRD\' has no parameterless constructor. I don\'

Answer 1

I don't understand why a parameterless constructor is even being called.

My guess is that you are populating ChildRequests lazily via a Linq/EF query, so the objects are not created until you iterate over them (which is done as part of the First method). At that point, EF tries to create an instance using a parameterless constructor which does not exist.

Answer 2

The error you get is pretty clear. You missed to define a parameterless constructor.

public class SLR : BaseEntity
{
    public SLR() : base
    {
    }

    // ...
    public virtual ICollection<SLRD> ChildRequests { get; set; }
}

The reason this is happens is the fact that your base class may have a parameterless constructor. So you have to define one for the derived class, SLR.