How to Serialize property of type ICollection<T> while using Entity Framework

Question

I have a class as shown below

public class Survey
    {
        public Survey()
        {
            SurveyResponses=new List<SurveyResponse>();
        }

        [Key]
        public Guid SurveyId { get; set; }
        public string SurveyName { get; set; }
        public string SurveyDescription { get; set; }
        public virtual ICollection<Question> Questions { get; set; }
        public virtual ICollection<SurveyResponse> SurveyResponses { get; set; }
    }

The above code gives me following exception

Cannot serialize member 'SurveyGenerator.Survey.Questions' of type 'System.Collections.Generic.ICollection

When i convert the ICollection to List it serializes properly

Since it is POCO of Entity Framework, i cannot convert ICollection to List

Answer 1

From the looks of your class the ICollection properties are defining foreign key relationships? If so, you wouldn't want to be publicly exposing the collections.

For example: If you are following the best practices guide for developing Entity Framework models, then you would have a separate class called "Question" which would wire up your two class together which might look like the following:

public class Question
{
    [Key]
    public int Id { get; set; }
    public string Title { get; set; }
    public string Description { get; set; }

    public virtual Survey Survey { get; set; }
}

If this was the case, you could quite possibly go round in circles calling the Question -> Survey -> ICollection -> Question

I had a similar incident using EF, MVC3 to implement a REST service and couldn't serialize the ICollection<> object then realised I didn't need to as I would be calling the object separately anyway.

The updated class for your purposes would look like this:

public class Survey
{
    public Survey()
    {
        SurveyResponses=new List<SurveyResponse>();
    }

    [Key]
    public Guid SurveyId { get; set; }
    public string SurveyName { get; set; }
    public string SurveyDescription { get; set; }

    [XmlIgnore]
    [IgnoreDataMember]
    public virtual ICollection<Question> Questions { get; set; }

    [XmlIgnore]
    [IgnoreDataMember]
    public virtual ICollection<SurveyResponse> SurveyResponses { get; set; }
}

I hopes this helps you out.