Asp.net-mvc – Web API Error: The ‘ObjectContent`1’ type failed to serialize the response body for content type

I am getting this error when attempting to use a Web API controller.

Web API Error: The 'ObjectContent`1' type failed to serialize the response body for content type

the code in my controller is as follows

public IEnumerable<Student> GetAllStudents()
    {
        var allstudents = unitOfWork.StudentRepository.Get(includeProperties: "Groups");


        return allstudents;
    }

    public Student GetStudentByID(Guid id)
    {
        return unitOfWork.StudentRepository.GetByID(id);
    }

and my 'Student' class is as follows

public partial class Student
{
    public Student()
    {
        this.Groups = new HashSet<Group>();
    }

    public System.Guid StudentID { get; set; }
    public string Surname { get; set; }
    public string FirstName { get; set; }
    public byte[] Timestamp { get; set; }

    public virtual Course Course { get; set; }
    public virtual ICollection<Group> Groups { get; set; }
}

Both methods result in the same error.

My inner exception is as follows

Type
'System.Data.Entity.DynamicProxies.Student_4C97D068E1AD0BA62C3C6E441601FFB7418AD2D635F7F1C14B64F4B2BE32DF9A'
with data contract name
'Student_4C97D068E1AD0BA62C3C6E441601FFB7418AD2D635F7F1C14B64F4B2BE32DF9A:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies'
is not expected. Consider using a DataContractResolver or add any
types not known statically to the list of known types – for example,
by using the KnownTypeAttribute attribute or by adding them to the
list of known types passed to DataContractSerializer.

I have a feeling I need to use the KnownType attribute but I'm not exactly sure how to implement it.

Any help would be appreciated