Imports <xmlns:co="http://schemas.microsoft.com/.NetConfiguration/v2.0">

Class editWebConfig
       Public shared Sub updateWebConfig()

              Dim PathToWebConfig As String = "d:\www\inetPub\web.config"

              Dim webConfig As XDocument = XDocument.Load(PathToWebConfig)
              
              Dim xNode = From p1 In webConfig.<co:configuration>.<co:connectionStrings>.<co:add> _
                                   Where p1.@name = "connectionString_Name_In_Web_Config" _
                                   Select p1
              
              xNode.@connectionString = "Data Source=.\SQLExpress;Initial Catalog=myDatabase;Integrated Security=True"

              webConfig.Save(PathToWebConfig)

       End Sub

End Class