Error trying to connect to Access from vb.net

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Error trying to connect to Access from vb.net

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#1 by (1 votes)

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What I am testing is how to insert data in access from vb.net.

For what I have, I made a test form with 2 fields plus a save button.

This is the code you make.

Imports System.Data.OleDb

Public Class Form1
Dim conexion As OleDbConnection
Dim comandos As OleDbCommand

Dim StrConnection As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Y:\db\TestDB.accdb"

Private Sub btnEnviar_Click(sender As Object, e As EventArgs) Handles btnEnviar.Click
    Try
        comandos = New OleDbCommand("INSERT INTO Tabla1 (campo1, campo2) VALUES (txtCampo1, txtCampo2)", conexion)
        comandos.Parameters.AddWithValue("@campo1", txtCampo1.Text)
        comandos.Parameters.AddWithValue("@campo2", txtCampo2.Text)

        comandos.ExecuteNonQuery()
        MsgBox("Guardado correctamente", vbInformation, "Correcto")

        txtCampo1.Clear()
        txtCampo2.Clear()
        txtCampo1.Focus()
    Catch ex As Exception
        MsgBox("Error al guardar", vbExclamation, "Error")
    End Try
End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Try
        conexion.ConnectionString = StrConnection
        conexion.Open()
        MsgBox("Conexión exitosa!", vbInformation, "Correcto")
    Catch ex As Exception
        MsgBox("Se ha producido un error al conectarse a DB" + ex.ToString, vbExclamation, "Error")
    End Try
End Sub

Private Sub btnSalir_Click(sender As Object, e As EventArgs) Handles btnSalir.Click
    'conexion.Close()
    MsgBox("Desconectado", vbInformation, "Correcto")
    Me.Close()
End Sub
End Class

What I get when trying to connect is a DBSystem.NullReferenceException. At first I thought that I did not have access to the Database, but I did connection tests and if I have access.

vb.net ms-access

asked by Luippo 03.10.2017 в 14:47

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score 1 · Accepted Answer

Good Luippo,

You have to instantiate the connection because right now you are not instantiating it, and then the exception jumps when you add some property:

Dim conexion As OleDbConnection 'Aqui solo estás declarando conexion como tipo OleDbConnection pero no la estas instanciando'

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Try
        conexion = new OleDbConnection() 'Instanciamos la conexión'
        conexion.ConnectionString = StrConnection
        conexion.Open()
        MsgBox("Conexión exitosa!", vbInformation, "Correcto")
    Catch ex As Exception
        MsgBox("Se ha producido un error al conectarse a DB" + ex.ToString, vbExclamation, "Error")
    End Try
End Sub