duplicate value in lists how can i avoid it :     Public Class clsA
    
        Public icounter As Integer
        Public dtime As DateTime
    
    End Class




     Dim list_A As New List(Of clsA)





                Dim dyus As DateTime = DateTime.Now
                oB = New clsA
                oB.dtime = dyus
                oB.counter = counter2 (comes from COM Port)

                Dim b As Integer = oB.counter

                Dim t1 As TimeSpan = New TimeSpan(0, 1, 0)

                list_A.Add(oB)
                

                If DateTime.Now - (list_A(0).dtime) > t1 Then
                    If list_A.Sum(Function(x) x.counter) > 10 Then
                        MessageBox.Show("TEST")
                    End If
                End If




hello,

list_A.Add(oB) has 2 values, time and counter.

and list_A is in timer. So it always increases, But

i want to avoid duplicate counters in this list.

How can i do that.






