Imports System.Data.OleDb
 
' me he creado un objeto para establecer la conexión
Public conexion_access As New OleDb.OleDbConnection
 
' cadena de conexión
conexion_access = New OleDbConnection(" Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Documents and Settings\carlos\Escritorio\Proyecto Ingegrado Carlos Barea Grado Superior\base de datos\Arcoclima.mdb")
 

Private Sub cbb_Marca_Prov_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbb_Marca_Prov.SelectedIndexChanged
        Dim i, j As Integer
        Dim marca_prov, id_prov_comp As String
 
        For i = 0 To ProveedoresTableAdapter.GetData.Rows.Count - 1
            marca_prov = ProveedoresTableAdapter.GetData.Rows(i).Item(3)
 
            For j = 0 To CompraTableAdapter.GetData.Rows.Count - 1
                id_prov_comp = CompraTableAdapter.GetData.Rows(j).Item(0)
 
                txt_Id_Proveedor_compra.Text = id_prov_comp
                Exit For
            Next
 
            Dim consulta As New OleDbCommand("SELECT Compra.Id_Proveedor FROM  Proveedores", conexion_access)
 
            conexion_access.Open()
           [color=red] txt_Id_Proveedor_compra.Text = CType(consulta.ExecuteNonQuery(), String)[/color]
        Next
    End Sub
 

Dim consulta As New OleDbCommand("SELECT Id_Proveedor FROM  Proveedores WHERE Marca = " & cbb_Marca_Prov.Text, conexion_access)