public void GetFamilyTypesInFamily(Document familyDoc)
{
    if (familyDoc.IsFamilyDocument)
    {
        FamilyManager familyManager = familyDoc.FamilyManager;

        // get types in family
        string types = "Family Types: ";
        FamilyTypeSet familyTypes = familyManager.Types;
        FamilyTypeSetIterator familyTypesItor = familyTypes.ForwardIterator();
        familyTypesItor.Reset();
        while (familyTypesItor.MoveNext())
        {
            FamilyType familyType = familyTypesItor.Current as FamilyType;
            types += "\n" + familyType.Name;
        }
        TaskDialog.Show("Revit",types);
    }
}

Public Sub GetFamilyTypesInFamily(familyDoc As Document)
    If familyDoc.IsFamilyDocument Then
        Dim familyManager As FamilyManager = familyDoc.FamilyManager

        ' get types in family
        Dim types As String = "Family Types: "
        Dim familyTypes As FamilyTypeSet = familyManager.Types
        Dim familyTypesItor As FamilyTypeSetIterator = familyTypes.ForwardIterator()
        familyTypesItor.Reset()
        While familyTypesItor.MoveNext()
            Dim familyType As FamilyType = TryCast(familyTypesItor.Current, FamilyType)
            types += vbLf + familyType.Name
        End While
        TaskDialog.Show("Revit", types)
    End If
End Sub