Código Button MySql

Imports MySql.Data.MySqlClient

Public Class frmcategoria

Private Sub bloquear()

txtcodigo.Enabled = True

btnalterar.Enabled = False

btnexcluir.Enabled = False

btnincluir.Enabled = False

End Sub

Private Sub frmcategoria_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

bloquear()

End Sub

Private Sub txtcodigo_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtcodigo.LostFocus

If txtcodigo.Text = Nothing Then

Exit Sub

End If

Dim cn As New MySqlConnection

cn.ConnectionString = My.Settings.lojaConnectionString

Dim cmd As New MySqlCommand

cmd.Connection = cn

cmd.CommandText = "select * from categoria where id_categoria=" & txtcodigo.Text

Try

cn.Open()

Dim dr As MySqlDataReader

dr = cmd.ExecuteReader

If dr.Read = True Then

txtcategoria.Text = dr("categoria")

cn.Close()

txtcodigo.Enabled = False

'liberamos os botões alterar e excluir

btnalterar.Enabled = True

btnexcluir.Enabled = True

btnincluir.Enabled = False

Else

txtcodigo.Text = "<AUT>"

txtcodigo.Enabled = False

' os botões são invertidos em realação a opção anterior'

btnalterar.Enabled = False

btnexcluir.Enabled = False

btnincluir.Enabled = True

End If

Catch ex As Exception

MsgBox("Ocorreu o erro: " & ex.Message, MsgBoxStyle.Critical)

End Try

End Sub

Private Sub txtcodigo_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtcodigo.TextChanged

End Sub

Private Sub GroupBox1_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GroupBox1.Enter

End Sub

Private Sub limpar()

txtcodigo.Clear()

txtcategoria.Clear()

txtcodigo.Focus()

End Sub

Private Sub btnincluir_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnincluir.Click

Dim cn As New MySqlConnection

cn.ConnectionString = My.Settings.lojaConnectionString

Dim comando As New MySqlCommand

comando.CommandText = "insert into categoria (categoria)" & _

"values ('" & txtcategoria.Text & "')"

Try

cn.Open()

comando.Connection = cn

comando.ExecuteNonQuery()

MessageBox.Show("Categoria incluída com sucasso!", "Inclusão")

cn.Close()

Catch ex As Exception

MessageBox.Show("Ocorreu o erro:" & ex.Message, "Erro", MessageBoxButtons.OK, MessageBoxIcon.Warning)

End Try

bloquear()

limpar()

End Sub

Private Sub btnalterar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnalterar.Click

Dim cn As New MySqlConnection