Sistema

Código vb.net
Imports System.Data.SqlClient
Module Generar
Public cn As New SqlConnection("Data source =NE-66C3FE7E80BA;" & _
"Initial Catalog =Examenfinal2;" & "integrated Security= true")
Public Function Generadores(ByVal TABLA As String) As String
Dim RESULT As String = ""
Dim DR1 As SqlDataReader
Dim ULT As Integer = 0
Dim CMD As NewSqlCommand("SELECT ultimo FROM generador WHERE parametro = '" + TABLA + "'", cn)
cn.Open()
DR1 = CMD.ExecuteReader
While DR1.Read
ULT = Val(DR1("ULTIMO") + 1)End While
cn.Close()

Dim CEROS As Integer
CEROS = 5 - Len(Str(ULT))
Select Case CEROS
Case 3 : RESULT = Left(TABLA, 1) + "000" +Trim(Str(ULT))
Case 2 : RESULT = Left(TABLA, 1) + "00" + Trim(Str(ULT))
Case 1 : RESULT = Left(TABLA, 1) + "0" + Trim(Str(ULT))
Case 0 : RESULT = Left(TABLA, 1) + "" +Trim(Str(ULT))
End Select
Generadores = RESULT
End Function
End Module

Public Class examen
Sub llenar()
Try
cn.Open()
Dim sql As NewSqlCommand("select * from profesor", cn)
Dim Reader As SqlDataReader
Reader = sql.ExecuteReader
Dim dt As New DataTable
dt.Load(Reader)Me.DataGridView1.DataSource = dt

cn.Close()

Catch ex As Exception
MessageBox.Show(ex.Message & "error fatal")
End Try
End Sub
Sub limpiar()Me.txtApe.Clear()
Me.txtmail.Clear()
Me.txtNomb.Clear()
Me.txtTel.Clear()
Me.txtTel.Clear()
Me.txtDire.Clear()
Me.comBcivil.ResetText()End Sub
Private Sub examen_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.txtCod.Text = Generadores("DOCUMENTO")
llenar()...