Problem from .NET 1.1 to 2.0... (Overload resolution failed...)

[bungpeng]

This code work fine in 1.1 but not 2.0. Any help? Thank you.

 

Dim Con As Object
       Dim sDB As String = "SQL"

       If sDB = "SQL" Then
           Con = New System.Data.SqlClient.SqlConnection
       Else
           Con = New System.Data.OleDb.OleDbConnection
       End If
       Con.Open("xxx")

 

I get this error:

System.MissingMemberException was unhandled by user code

Message="Overload resolution failed because no accessible 'Open' accepts this number of arguments."

Source="Microsoft.VisualBasic"

StackTrace:

at Microsoft.VisualBasic.CompilerServices.OverloadResolution.ResolveOverloadedCall(String MethodName, MemberInfo[] Members, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, BindingFlags LookupFlags, Boolean ReportErrors, ResolutionFailure& Failure)

at Microsoft.VisualBasic.CompilerServices.NewLateBinding.ResolveCall(Container BaseReference, String MethodName, MemberInfo[] Members, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, BindingFlags LookupFlags, Boolean ReportErrors, ResolutionFailure& Failure)

at Microsoft.VisualBasic.CompilerServices.NewLateBinding.CallMethod(Container BaseReference, String MethodName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack, BindingFlags InvocationFlags, Boolean ReportErrors, ResolutionFailure& Failure)

at Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateCall(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack, Boolean IgnoreReturn)

at _Default.Page_Load(Object sender, EventArgs e) in C:\Documents and Settings\bpchia\My Documents\Visual Studio 2005\WebSites\WebSite1\Default.aspx.vb:line 16

at System.Web.UI.Control.OnLoad(EventArgs e)

at System.Web.UI.Control.LoadRecursive()

at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

[PlausiblyDamp]

As a quickie - you could declare Con as System.Data.IDbConnection rather than object, at least then you will get intellisense to help you.

[bungpeng]

What if in other case, it does not have something like .IDbConnection object?

It is not possible to create 'object' variable and assign object to it later?

[PlausiblyDamp]

If you have a variable called 'Con' and the two options you present both assign a database connection to it (which means they implement IDbConnection) why would 1) I assume it was meant to hold anything other than a database connection or 2) you want to store anything other than a database connection in it?

[bungpeng]

No, I mean what if I create 2 similar classes and object refer to one of it dynamically?

[PlausiblyDamp]

Define a common interface that both classes implement and declare your variable as that interface.

 

Interface IExample
   Sub ExampleSub()
   Function ExampleFunction(ByVal exampleParameter As String) as String
End Interface

Class ExampleOne
   Implements IExample

   Public Function ExampleFunction(ByVal exampleParameter As String) As string Implements IExample.ExampleFunction
return string.Empty
   End Function

   Public Sub ExampleSub() Implements IExample.ExampleSub

   End Sub
End Class

Class ExampleTwo
   Implements IExample

   Public Function ExampleFunction(ByVal exampleParameter As String) As string Implements IExample.ExampleFunction
       Return String.Empty
   End Function

   Public Sub ExampleSub() Implements IExample.ExampleSub

   End Sub
End Class

 

You can then use this like

       Dim ex As IExample

       If True Then
           ex = New ExampleOne
       Else
           ex = New ExampleTwo
       End If

       ex.ExampleSub()

[bungpeng]

oic

Thank you very much!