Knowledge Base

HOW TO: Build a Connection String Programmatically in ADO.NET by Using Visual C++ .NET

Article ID: 310084

Article Last Modified on 11/29/2007

APPLIES TO

Microsoft ADO.NET 1.0
Microsoft ADO.NET 1.1
Microsoft Visual C++ .NET 2002 Standard Edition
Microsoft Visual C++ .NET 2003 Standard Edition

This article was previously published under Q310084

Caution ADO and ADO MD have not been fully tested in a Microsoft .NET Framework environment. They may cause intermittent issues, especially in service-based applications or in multithreaded applications. The techniques that are discussed in this article should only be used as a temporary measure during migration to ADO.NET. You should only use these techniques after you have conducted complete testing to make sure that there are no compatibility issues. Any issues that are caused by using ADO or ADO MD in this manner are unsupported. For more information, see the following article in the Microsoft Knowledge Base:

840667 You receive unexpected errors when using ADO and ADO MD in a .NET Framework application

For a Microsoft Visual Basic .NET version of this article, see 309485.
For a Microsoft Visual C# .NET version of this article, see 310083.

This article refers to the following Microsoft .NET Framework Class Library namespace:

System.Data.OleDb

IN THIS TASK

SUMMARY

Requirements
Create an ADO Connection
Create an OLE DB Connection
Additional Information

REFERENCES

SUMMARY

This step-by-step article describes how to use the Data Link Properties dialog box to programmatically create a connection string at design time.

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Requirements

The following list outlines the recommended hardware, software, network infrastructure, and service packs that you need:

Microsoft Windows 2000 Professional, Windows 2000 Server, Windows 2000 Advanced Server, or Windows NT 4.0 Server
Microsoft Visual Studio .NET

This article assumes that you are familiar with the following topics:

Visual Studio .NET
ADO.NET fundamentals and syntax
ActiveX Data Objects (ADO) fundamentals and syntax

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Create an ADO Connection

Start Visual Studio .NET and create a new Managed C++ Application. Name it CreateDL.

Replace the default code in CreateDL.cpp with the following code:

#include "stdafx.h"
#include <stdio.h>

#undef EOF
#import "c:\program files\common files\system\ole db\oledb32.dll" rename_namespace("dlinks")
#import "c:\program files\common files\system\ado\msado15.dll" rename_namespace("ado")

void TestConnection(void);

#ifdef _UNICODE
int wmain(void)
#else
int main(void)
#endif
{
    TestConnection();
    return 0;
}

void TestConnection(void)
{
    using namespace dlinks;
    using namespace ado;
    
    HRESULT hr;
    ::CoInitialize( NULL );
    IDataSourceLocatorPtr dlPrompt = NULL;
    _ConnectionPtr conn = NULL;
    hr = dlPrompt.CreateInstance(__uuidof(DataLinks));
    conn = dlPrompt->PromptNew();
    if ( NULL != conn )
    {
        printf( "Connect: %s\n", (char*) conn->ConnectionString );
    }
   
    return;
}

On the Debug menu, click Start without Debugging to run the project.
Type the appropriate information in the Data Link Properties dialog box, and make sure that you click to select the Allow Saving Password check box.
Click Test Connection.
Click OK. If the connection test succeeded in the data link, a connection to the database is established, and a message box is displayed.

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Create an OLE DB Connection

When you create an OLE DB connection with the OLE DB managed provider in .NET, you cannot create connections to ODBC datasources. Because ODBC has its own Managed provider in .NET, you receive an error if you use the Microsoft OLE DB provider for ODBC drivers option in the Data Link Properties dialog box. Additionally, you must load ADO into the application because the data link creates an ADODB Connection object that is not compatible with the OLEDBConnection object. Therefore, you must create an ADODB Connection and assign its ConnectionString property to the ConnectionString property of the OLEDBConnection object for this to work correctly.

1. Start Microsoft Visual Studio .NET, and create a new Managed C++ Application project. Name it OledbDL.cpp.

Replace the default code in OledbDL.cpp with the following code:

#using <mscorlib.dll>
#using <System.dll>
#using <System.Data.dll>

#undef EOF
#import "c:\program files\common files\system\ole db\oledb32.dll" rename_namespace("dlinks")
#import "c:\program files\common files\system\ado\msado15.dll" rename_namespace("ado")

void TestConnection(void);

#ifdef _UNICODE
int wmain(void)
#else
int main(void)
#endif
{
    TestConnection();
    return 0;
}

void TestConnection(void)
{
    using namespace dlinks;
    using namespace ado;
    using namespace System; 
         using namespace System::Data::OleDb;
    
    HRESULT hr;
    ::CoInitialize( NULL );
    IDataSourceLocatorPtr dlPrompt = NULL;
    OleDbConnection *oleConn = new OleDbConnection();
    _ConnectionPtr adoConn = NULL;
    hr = dlPrompt.CreateInstance(__uuidof(DataLinks));
    adoConn = dlPrompt->PromptNew();
    System::String *str = (char*) adoConn->ConnectionString; // define a garbage collected string
    oleConn->ConnectionString = str;

    try
    {
        oleConn->Open();
        if ( NULL != oleConn )
        {
        Console::WriteLine("Connect: {0}\n",  oleConn->ConnectionString );
        }
    }
    catch(Exception *ex)
    {
        Console::WriteLine(ex->Message);
    }
    __finally
    {
        oleConn->Close();
    }
    return;
}

On the Debug menu, click Start without Debugging to run the project.
Type the appropriate information in the Data Link Properties dialog box, and make sure that you click to select the Allow Saving Password check box.
Click Test Connection.
Click OK. If the connection test succeeded in the data link, a connection to the database is established, and a message box is displayed.

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Additional Information

It requires additional effort to use this method to create an ODBC connection because the data link creates a connection string that is specific to OLE DB and is not compatible with the ODBC managed provider. For this to work, you must parse the ADODB connection string for the relevant information such as the user ID, password, and data source. After you obtain this information, you can use it to create a connection string that is specific to ODBC. Keep in mind that the data link only uses ODBC data source names (DSNs); therefore, you cannot create a DSN-less connection through the data link.

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REFERENCES

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

286189 HOWTO: Invoke the OLE DB Data Link Properties Dialog Box in Visual Basic Code

283245 HOWTO: Persist Data Links Programmatically

193128 HOWTO: Create an ODBC and OLEDB Connection Prompt Control in ADO

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Keywords: kbhowtomaster KB310084

Microsoft KB Archive/310084

Contents

HOW TO: Build a Connection String Programmatically in ADO.NET by Using Visual C++ .NET

IN THIS TASK

SUMMARY

Requirements

Create an ADO Connection

Create an OLE DB Connection

Additional Information

REFERENCES