This article demonstrates how to use an OLE DB Universal Data Link (.udl) file to specify the connection string that an ADO.NET OleDbConnection object uses to establish a database connection.

OLE DB Universal Data Link (.udl) files provide a convenient way to create and verify an ActiveX Data Objects (ADO) connection string that is used to connect to an OLE DB data source. The connection string information is persisted in a specific format to a file with the .udl extension. You can reference a .udl file in the ConnectionString property of an ADO.NET OleDbConnection object to specify the connection string that the object should use to connect to a database. Use the File Name parameter of the connection string to specify the name of the .udl file that contains the connection string information.

Steps to Build the Sample

Follow these steps to create a Managed C++ Application project that uses a .udl file to specify the connection string information for an ADO.NET OleDbConnection object:

1. Use the SQL Server OLE DB Provider to connect to one of your Microsoft SQL Server databases, and create a .udl file named Test.udl in the root folder of drive C.
   
   You can also use the Microsoft OLE DB Provider for Jet 4.0 to configure the .udl file to connect to a Microsoft Access 97 or 2000 database if you do not have access to a SQL Server database.For additional information about how to create a .udl file, click the article number below to view the article in the Microsoft Knowledge Base:
   189680  (http://kbalertz.com/Feedback.aspx?kbNumber=189680/EN-US/ ) How To Use Data Link Files with ADO
2. Open a new Managed C++ Application project.
3. In Solution Explorer, double-click the .cpp file.
4. Replace the default code in the source (.cpp) file with the following code:

   #include "stdafx.h"
   
   #using <mscorlib.dll>
   #using <System.dll>
   #using <System.Data.dll>
   
   using namespace System;
   using namespace System::Data;
   using namespace System::Data::OleDb;
   
   // This is the entry point for this application.
   #ifdef _UNICODE
   int wmain(void)
   #else
   int main(void)
   #endif
   {
   	String *constr = "File Name=c:\\test.udl";
   	OleDbConnection *myConnection = new OleDbConnection(constr);
   
   	try
   	{
       	myConnection->Open();
   		if (myConnection->State == ConnectionState::Open)
   			Console::WriteLine("Connection opened successfully");
   		else
   			Console::WriteLine("Connection could not be established");
   	}
   	catch(Exception *ex)
   	{
   		Console::Write(ex->Message);
   	}
   	__finally
   	{
                     myConnection->Close();
   	}
   
   	return 0;
   }
   					

5. In the statement that sets the ConnectionString property of the OleDbConnection object, modify the path to the .udl file if you created it with a different name or persisted it to a different location.
6. Run the application from within the Visual Studio .NET Integrated Development Environment (IDE). Success or failure is indicated in the console window.
7. Press any key to dismiss the console window and stop the application.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base: