Dll Function is not appearing in vb 2015 project

Using VS 2015 on Server 2012 R2

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DLL Code is

Public Class SalDll
    Class SubClass1
        Function AddingNumbers(ByVal Number1 As Integer, ByVal Number2 As Integer)
            Return (Number1 + Number2)
        End Function
    End Class
End Class

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Project Code is

Imports Test1.SalDll
Public Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        SubClass1.(the problem is here)
    End Sub
End Class

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The problem is
By typing (Imports Test1.) then (SalDll) appears and I can select
By typing (SubClass1.) then (AddingNumbers) is not appearing

Any Idea