What mistake am I making when creating a constraint in generics?

Question

In asp.net 2.0 I have several "dropdowns" defined using generics (examples eye color, hair color, etc). The fields are all typical; id, text, etc. All are defined as their own classes which must implement an interface I created called ILookup. However, when I try to return a List<> of this class using:

ddlEyeColor.DataSource = luMgt.GetLookUpItemList(Of EyeColor)()

which calls the BC layer:

  Public Function GetLookUpItemList(Of t As {ILookup, New})() As List(Of t)
    Dim luMgt As New LookupMgt
    Return luMgt.GetLookUpItemList(Of t)()
End Function

Which calls the DBC layer which, in part is....

    Public Function GetLookUpItemList(Of t As {ILookup, New})() As List(Of t)

    Dim lstGenericList As New List(Of t)
    'rest of code to populate the list here
    end function

the error message claims EyeColor does not implement ILookup.

Error 21 Type argument 'EyeColor' does not inherit from or implement the constraint type 'ILookup'.

But here is the beginning of the EyeColor class....

Public Class EyeColor
Implements ILookup

Here is the complete Interface....

Public Interface ILookup

Property ID() As Int32
Property Text() As String
Property Description() As String
Property Status() As Status
Property OrderID() As Int32
ReadOnly Property LookUpType() As LookUpType

End Interface

And here, in the EyeColor class, I am implementing the properies of the interface

Public Overrides Property Description() As String Implements ILookup.Description
    Get
        Return MyBase.Description
    End Get
    Set(ByVal value As String)
        MyBase.Description = value
    End Set
End Property

Public Overrides Property ID() As Integer Implements ILookup.ID
    Get
        Return MyBase.ID
    End Get
    Set(ByVal value As Integer)
        MyBase.ID = value
    End Set
End Property

Public Overrides Property OrderID() As Integer Implements ILookup.OrderID
    Get
        Return MyBase.OrderID
    End Get
    Set(ByVal value As Integer)
        MyBase.OrderID = value
    End Set
End Property

Public Overrides Property Status() As Status Implements ILookup.Status
    Get
        Return MyBase.Status
    End Get
    Set(ByVal value As Status)
        MyBase.Status = value
    End Set
End Property

Public Property EyeColor() As String Implements ILookup.Text
    Get
        Return _eyeColor
    End Get
    Set(ByVal value As String)
        _eyeColor = value
    End Set
End Property

Public ReadOnly Property LookUpType() As LookUpType Implements ILookup.LookUpType
    Get
        Return BE.LookUpType.EyeColor
    End Get
End Property

Answer 1

I upvoted Jay's comment. He's absolutely right. Simply adding Implements ILookup to your class definition doesn't actually implement the interface.

You need to create the actual methods that the interface dictates.

Answer 2

I think you need to change your method signature to:

Public Function GetLookUpItemList(Of T As {ILookup, New})() As List(Of ILookup)