Serializing entity to XML - add method - asp.net-mvc

Question

Can anybody help me with the below?
Models
public class Integer
{
public int IntegerID { get; set; }
[Required(ErrorMessage = "Enter an integer")]
[Integer(ErrorMessage = "Enter an integer")]
public int IntegerValue { get; set; }
public int IntegerListID { get; set; }
public virtual IntegerList IntegerList { get; set; }
}
public class IntegerList
{
public int IntegerListID { get; set; }
public string Direction { get; set; }
public long Performance { get; set; }
public virtual ICollection<Integer> Integers { get; set; }
public IntegerList()
{
Integers = new List<Integer>();
}
}
Controller Action
public ActionResult XMLexport () {
Object obj = db.IntegerLists.Include("Integers");
Serialize(obj);
return View();
}
public static string Serialize(Object obj)
{
DataContractSerializer serializer = new DataContractSerializer(obj.GetType());
MemoryStream memoryStream = new MemoryStream();
serializer.WriteObject(memoryStream, obj);
return Encoding.UTF8.GetString(memoryStream.GetBuffer());
}
At the line
serializer.WriteObject(memoryStream, obj);
I'm getting the error:
Type 'System.Data.Entity.Infrastructure.DbQuery`1[[IntegerSorter.Models.IntegerList, IntegerSorter, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' is an invalid collection type since it does not have a valid Add method with parameter of type 'IntegerSorter.Models.IntegerList'.
Can somebody advise me where and how to implement the Add method?
Update:
Changing:
Object obj = db.IntegerLists.Include("Integers");
to
Object obj = db.IntegerLists.Include("Integers").ToList();
results in:
Type 'System.Data.Entity.DynamicProxies.IntegerList_62F0932A6DFC38A25629DF18911498D42B3785A93BCE8B8D2F77C3363B3F4200' with data contract name 'IntegerList_62F0932A6DFC38A25629DF18911498D42B3785A93BCE8B8D2F77C3363B3F4200: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.

Answer 1

Try changing this line:
Object obj = db.IntegerLists.Include("Integers");
To this:
Object obj = db.IntegerLists.Include("Integers").ToList();
This will cause the database query to run and give you a List<IntegerList> instead of a DbQuery<IntegerList>. This should then provide what the serializer wants (because it has a Add(IntegerList) method available as requested by the error).

Answer 2

I've accepted Greg's answer but feel I should detail the subsequent issues I had to work through:
Type 'System.Data.Entity.DynamicProxies.IntegerList_62F0932A6DFC38A25629DF18911498D42B3785A93BCE8B8D2F77C3363B3F4200' with data contract name 'IntegerList_62F0932A6DFC38A25629DF18911498D42B3785A93BCE8B8D2F77C3363B3F4200: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.
was solved with:
Context.Configuration.ProxyCreationEnabled = false;
and then:
Object graph for type 'System.Collections.Generic.List`1[[IntegerSorter.Models.Integer, IntegerSorter, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' contains cycles and cannot be serialized if reference tracking is disabled.
was solved by decorating the navigation property on the Integer class as below:
[IgnoreDataMember]
public virtual IntegerList IntegerList { get; set; }