Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim i, n, j As Integer
        j = 1
        n = DropDownList1.Items.Count

        If n = 0 Then
            DropDownList1.Items.Add(TextBox1.Text)

        Else
            For i = 0 To n - 1
                If TextBox1.Text = DropDownList1.Items(i).Text Then
                    j = j + 1
                End If
            Next
            If j = 2 Then
                MsgBox("Already available")
            Else
                DropDownList1.Items.Add(TextBox1.Text)
            End If
        End If
    End Sub