Ben 10 Alien Force Ep 1 Megaviedo

independent data access provider to automatically associate

Hola

Algo que aunque no siempre sea aplicable a la realidad, todos deseamos, es poder tener un programa al cual le podamos cambiar de BD y que todo siga funcionando de forma automática sin mayores traumas en el código fuente, sin mucha charla les comento que desde el framework 2.0 esto es posible con ado.net a través de las clases que se encuentran en el espacio de nombre System.Data.Common

Como es el procedimiento?

• Recuperar el proveedor de data and the connection string from somewhere and create a DbProviderFactory
• Use that to create DataAdapters provider through DbProviderFactory.CreateDataAdapter ()
• use
DataAdapters

Creating the connection I'll be
too simplistic just to bring some order and structure code depends on where you put the strings that return the following methods

Public Shared GetProvider Function ( ) As String
Return "System.Data.SqlClient"
End Function

Public Shared Function GetCnnString() As String
Return "Data Source=MiSQLsrv;Initial Catalog=MiBD;Integrated Security = True "
End Function

above functions should be making access to app.config or a text file which the channels recovered up the show as constants

We'll use them, creating a connection from the supplier, so that the connection is indicated for the supplier whose description is obtained GetProvider function () Dim

sProv As String = GetProvider()
Dim sCnn As String = GetCnnString()

Dim

oCnn As DbConnection = nothing

Dim f As DbProviderFactory = DbProviderFactories.GetFactory(sProv)
oCnn= f.CreateConnection()
oCnn.ConnectionString = sCnn

Now that we have the connection we must generate the commands to run a select query.

Dim cmd As DbCommand = oCnn.CreateCommand ()

cmd.CommandText = "Select * from myTable where id = 1" cmd
. CommandType = CommandType.Text

oCnn.Open ()

Dim dr As DbDataReader = cmd.ExecuteReader
Dim ID As Integer=0
Dim sNombres As String=""

If dr.HasRows Then

dr.Read()
dim ID as integer = dr( "Id" )
sNombres = dr( "Nombres" )

End If

dr.Close()
oCnn.Close()

As you saw the connection used to generate a command, which will depend on the supplier, then I give the text of the query and then get a datareader from which to download the data to variables finally close the DataReader and connection

You see the issue of vendor independence is not as otherworldly as if not more it is really easy. In another article (which I guess will be this year) will show you how to use DataAdapters to record data in a structure similar to this.

I hope this helps someone you

soon and Happy Holidays! Salu2

Sergio