How To Execute Distributed Transaction Using ODBC API with SQL Server

/*
Assume the following TestDistributedTransaction table exists on both the servers.
Create this table before running this sample.


if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[TestDistributedTransaction]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[TestDistributedTransaction]
GO

CREATE TABLE [dbo].[TestDistributedTransaction] (
	[Col1] [int] NULL ,
	[Col2] [varchar] (100) NULL 
) ON [PRIMARY]
GO
*/ 

#include <windows.h>
#include <stdio.h>
#include <oledb.h>
#include <oledberr.h>
#include <txdtc.h>
#include <xolehlp.h>
#include <sql.h>
#include <sqlext.h>
#include <Odbcss.h>


void main()
{
	HRESULT hr;
	ITransactionDispenser *pTransactionDispenser = NULL;
	ITransaction * pITransaction;
	SQLHDBC hdbc = NULL;
   	SQLHENV		henv;
   	SQLHDBC		hdbc1;
   	SQLHDBC		hdbc2;
   	SQLHSTMT	hstmt1;
   	SQLHSTMT	hstmt2;
	SQLRETURN   sr;


   	//SQLRETURN	hr;
   	SQLCHAR*	theDiagState = new SQLCHAR[50];
   	SQLINTEGER	theNativeState;
   	SQLCHAR*	theMessageText  = new SQLCHAR[255];
   	SQLSMALLINT	iOutputNo;
   	short		iStringLength2;
   	char		sOutConnectionString[1000];

	//CoInitialize call is not needed for DtcGetTransactionManager call, but if you are using the other
	//OLE object, you need to call it first.
	//hr = CoInitialize( NULL );

   	// Allocate two different hdbc handles. We will connect to two different computers that are running SQL Server.
   	hr = SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&henv);
   	hr = SQLSetEnvAttr(henv,SQL_ATTR_ODBC_VERSION,(SQLPOINTER) SQL_OV_ODBC3,0);
   	hr = SQLAllocHandle(SQL_HANDLE_DBC,henv,&hdbc1);
   	hr = SQLAllocHandle(SQL_HANDLE_DBC,henv,&hdbc2);

	//Get the Distributed Transaction Coordinator Manager.
	hr = DtcGetTransactionManager(NULL, NULL,
			IID_ITransactionDispenser, 0, 0, NULL,
			(void**) &pTransactionDispenser);
	
	//Connecting to first server.
   	hr = SQLDriverConnect(hdbc1,NULL,(SQLCHAR*)"DSN=YourDSN#1;uid=USERID;pwd=PASSWORD" ,SQL_NTS, (SQLCHAR*) sOutConnectionString,100,&iStringLength2,SQL_DRIVER_NOPROMPT);
   	if (hr != SQL_SUCCESS)
   	{
   		SQLGetDiagRec(SQL_HANDLE_DBC,hdbc1,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
   	}

	//Connecting to second server.
	hr = SQLDriverConnect(hdbc2,NULL,(SQLCHAR*) "DSN=YourDSN#2;uid=UID;pwd=PASSWORD" ,SQL_NTS,(SQLCHAR*) sOutConnectionString,100,&iStringLength2,SQL_DRIVER_NOPROMPT);
   	if (hr != SQL_SUCCESS)
   	{
   		SQLGetDiagRec(SQL_HANDLE_DBC,hdbc2,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
   	}


	//Start the transaction on DTC.
	hr = pTransactionDispenser->BeginTransaction (
			NULL,		// Controlling IUnknown
			ISOLATIONLEVEL_READCOMMITTED,	// Isolation level
			0,				// Isolation Flags
			NULL,			// Reserved
			&pITransaction);	// Ptr to the Transaction Object


	//Enlist the two connections (hdbc) in DTC.
	//You need to do this AFTER you make the connection (for example, after you call SQLDriverConnect or SQLConnect).
	hr = SQLSetConnectAttr(hdbc1,
             SQL_COPT_SS_ENLIST_IN_DTC,
                 (SQLPOINTER)pITransaction,SQL_IS_INTEGER);

 	if (hr != SQL_SUCCESS)
   	{
 			SQLGetDiagRec(SQL_HANDLE_DBC,hdbc1,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
			 printf( "Error :%s\n", theMessageText);
  	}
	
	hr =SQLSetConnectAttr(hdbc2,
             SQL_COPT_SS_ENLIST_IN_DTC,
                 (SQLPOINTER)pITransaction,SQL_IS_INTEGER);

 	if (hr != SQL_SUCCESS)
   	{
   			SQLGetDiagRec(SQL_HANDLE_DBC,hdbc2,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
			printf( "Error :%s\n", theMessageText);
   	}

	//Allocate statement handle and run a query.
	hr = SQLAllocHandle(SQL_HANDLE_STMT,hdbc1,&hstmt1);
	hr = SQLAllocHandle(SQL_HANDLE_STMT,hdbc2,&hstmt2);

    hr = SQLExecDirect(hstmt1, (SQLCHAR*) "Insert Into TestDistributedTransaction (Col1, Col2) Values (1,'Test 1')", SQL_NTS);
  	if (hr != SQL_SUCCESS)
   	{
   		SQLGetDiagRec(SQL_HANDLE_STMT,hstmt1,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
		printf( "Error :%s\n", theMessageText);
		pITransaction->Abort(NULL,FALSE,FALSE);
		
   	}
	else
	{

	//Allocate and run the second query in the second server

		hr = SQLExecDirect(hstmt2, (SQLCHAR*) "Insert Into TestDistributedTransaction (Col1, Col2) Values (1,'Test 2')", SQL_NTS);
  		if (hr != SQL_SUCCESS)
   		{
			SQLGetDiagRec(SQL_HANDLE_STMT,hstmt2,1,(SQLCHAR*)theDiagState,&theNativeState,(SQLCHAR*)theMessageText,100,&iOutputNo);
			pITransaction->Abort(NULL,FALSE,FALSE);
   		}
		else
		{
			hr = pITransaction->Commit( 0, XACTTC_SYNC_PHASEONE, 0 );
		}


	}
	
	pITransaction->Release();
 	
   	hr = SQLFreeHandle(SQL_HANDLE_STMT,hstmt1);
	hr = SQLDisconnect(hdbc1);
	hr = SQLFreeHandle(SQL_HANDLE_STMT,hstmt2);
	hr = SQLDisconnect(hdbc2);
   	hr = SQLFreeHandle(SQL_HANDLE_DBC,hdbc1);
   	hr = SQLFreeHandle(SQL_HANDLE_DBC,hdbc2);
   	hr = SQLFreeHandle(SQL_HANDLE_ENV,henv);
	//CoUninitialize();
}