C#

// datagrid1 has objects from list1
// datagrid2 has objects from list2
foreach (CustomObject a in list1)
{
    if (!list2.Contains(a))
    {
        //It is not in the list so we want to make a note of it
        notIncludedList.Add(a);
    }
}
//How many rows in list1 don't exist in list2?
int num = notIncludedList.count;

Class MyClasss
    Implements ICloneable

    Private pName As String
    Public Property Name() As String
        Get
            Return pName
        End Get
        Set(ByVal value As String)
            pName = value
        End Set
    End Property

    Private pNAmes As New List(Of String)
    Public Property Names() As List(Of String)
        Get
            Return pNAmes
        End Get
        Set(ByVal value As List(Of String))
            pNAmes = value
        End Set
    End Property

    Public Function Clone() As Object Implements ICloneable.Clone

        Dim result As New MyClasss
        result = Me.MemberwiseClone

        ' If I have any properties of collection type
        ' I need to create a copy of each list 
        Dim TempNames As New List(Of String)
        For Each str As String In Names
            TempNames.Add(str)
        Next

        result.Names = TempNames
        Return result

    End Function
End Class

static object Clone( object parent ) {

   XmlSerializer serializer = new XmlSerializer( parent.GetType() );
   object clone = null;

   using ( MemoryStream stream = new MemoryStream() ) {
      serializer.Serialize( stream, parent );
      stream.Position = 0;
      clone = serializer.Deserialize( stream );
   }  //  end using.

   return clone;
}