How to auto generate ID with character in VB.Net?

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VB

How to auto generate ID with charactor in VB.Net?
for Example : "C-00001", "SV-1"

if this method is correct then how to contain charactor in this Method:
( for Example : "AREA-1" )

Private Sub auto()

        con = New SqlConnection(cs)
        con.Open()

        Dim ct As String = "select Max(NUM) as NUMS from AREAs"
        cmd = New SqlCommand(ct)
        cmd.Connection = con

        rdr = cmd.ExecuteReader()
        rdr.Read()

        If rdr("NUMS").ToString() <> "" Then
            txtSerID.Text = Integer.Parse(rdr("NUMS").ToString()) + 1
        Else
            txtSerID.Text = 1
        End If
        rdr.Close()
        If con.State = ConnectionState.Open Then
            con.Close()
        End If
        con.Close()
    End Sub

If this method is correct/OK then how to contain character in this Method:
( for Example : "AREA-1"