ASP.NET

Unable to cast the type 'System.Linq.IQueryable`1' to type 'System.Collections.Generic.IEnumerable`1'. LINQ to Entities only supports casting Entity Data Model primitive types.

The cast to value type 'Boolean' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.

t.checkvalue = iif(t.checkvalue<>nothing,t.checkvalue,false) 

public class DbTestClass
    {
        public void Test()
        {
            using (var context = new Model.ParadiseEntities())
            {
                var items = from s in context.Survey3D.Take(5)
                            select new Testing
                            {
                                TestId = s.Id,
                                Items = from v in context.Volumes where v.Survey3D_Id == s.Id select v,
                                Items1 = from v in context.Volumes where v.Survey3D_Id == s.Id select v,
                                Items2 = from v in context.Volumes where v.Survey3D_Id == s.Id select v,
                                Items3 = from v in context.Volumes where v.Survey3D_Id == s.Id select v,
                                Item = context.Volumes.Where(a => a.Survey3D_Id == s.Id).FirstOrDefault()
                            };
                var list = items.ToList();
            }
        }
    }

    [DataContract]
    public class Testing
    {
        [DataMember]
        public Guid TestId { get; set; }
        [DataMember]
        public IEnumerable<Volume> Items { set; get; }
        [DataMember]
        public IEnumerable<Volume> Items1 { set; get; }
        [DataMember]
        public IEnumerable<Volume> Items2 { set; get; }
        [DataMember]
        public IEnumerable<Volume> Items3 { set; get; }
        [DataMember]
        public Volume Item { get;set; }

    }

Public Class DbTestClass
	Public Sub Test()
		Using context = New Model.ParadiseEntities()
			Dim items = From s In context.Survey3D.Take(5)New Testing() With { _
				Key .TestId = s.Id, _
				Key .Items = From v In context.Volumes Where v.Survey3D_Id = s.Idv, _
				Key .Items1 = From v In context.Volumes Where v.Survey3D_Id = s.Idv, _
				Key .Items2 = From v In context.Volumes Where v.Survey3D_Id = s.Idv, _
				Key .Items3 = From v In context.Volumes Where v.Survey3D_Id = s.Idv, _
				Key .Item = context.Volumes.Where(Function(a) a.Survey3D_Id = s.Id).FirstOrDefault() _
			}
			Dim list = items.ToList()
		End Using
	End Sub
End Class

<DataContract> _
Public Class Testing
	<DataMember> _
	Public Property TestId() As Guid
		Get
			Return m_TestId
		End Get
		Set
			m_TestId = Value
		End Set
	End Property
	Private m_TestId As Guid
	<DataMember> _
	Public Property Items() As IEnumerable(Of Volume)
		Get
			Return m_Items
		End Get
		Set
			m_Items = Value
		End Set
	End Property
	Private m_Items As IEnumerable(Of Volume)
	<DataMember> _
	Public Property Items1() As IEnumerable(Of Volume)
		Get
			Return m_Items1
		End Get
		Set
			m_Items1 = Value
		End Set
	End Property
	Private m_Items1 As IEnumerable(Of Volume)
	<DataMember> _
	Public Property Items2() As IEnumerable(Of Volume)
		Get
			Return m_Items2
		End Get
		Set
			m_Items2 = Value
		End Set
	End Property
	Private m_Items2 As IEnumerable(Of Volume)
	<DataMember> _
	Public Property Items3() As IEnumerable(Of Volume)
		Get
			Return m_Items3
		End Get
		Set
			m_Items3 = Value
		End Set
	End Property
	Private m_Items3 As IEnumerable(Of Volume)
	<DataMember> _
	Public Property Item() As Volume
		Get
			Return m_Item
		End Get
		Set
			m_Item = Value
		End Set
	End Property
	Private m_Item As Volume

End Class