Microsoft Visual C++ .NET Professional Projects - Premier Press

Any class that needs to use the COM+ services will have to derive from the ServicedComponent class. Add the following declaration, too:

using System::EnterpriseServices::ServicedComponent;

public __gc class Class1: public ServicedComponent

{

To specify that the class will be using transactions, use the Transaction attribute:

[Transaction(TransactionOption::Required)]

public __gc class Class1: public ServicedComponent

{

// TODO: Add your methods for this class here.

};

The Transaction attribute can have the following values:

TransactionOption::Required. This creates a new transaction if the calling application is not in a transaction.

TransactionIsolationLevel::Serializable. This prevents modification of data until the transaction is complete.

Timeout. This is used to specify the time after which the transaction should abort.

To the class Class1, add a new method updateOrders with the following signature:

public:

int updateOrders(String *strProdID,String *strCustID, String *strSessionID, String

*strOrderDate, String *strOrderStatus)

{

802 Project 8 .NET ASSEMBLIES WITH MANAGED C++ AND .NET

This method first needs to insert a record into the Orders table. You have already seen how this can be easily achieved using the SQL Server .NET Provider:

//Create a Connection object

SqlConnection *sConn=new SqlConnection();

//Initialize and open the connection string sConn->set_ConnectionString(“Data Source=Server1;Initial Catalog=ArtShop;Integrated Security=SSPI”);

//Open the connection sConn->Open();

SqlDataAdapter *dataAdapter=new SqlDataAdapter();

String *strCmd;

try{

//Construct the command string.

strCmd=”insert into Orders(ProdId,CustId,SessionID,OrderDate,OrderStatus) values(“;

strCmd=strCmd->Concat(strCmd,strProdID); strCmd=strCmd->Concat(strCmd,”,”); strCmd=strCmd->Concat(strCmd,strCustID); strCmd=strCmd->Concat(strCmd,”,’”); strCmd=strCmd->Concat(strCmd,strSessionID); strCmd=strCmd->Concat(strCmd,”’,’”); strCmd=strCmd->Concat(strCmd,strOrderDate); strCmd=strCmd->Concat(strCmd,”’,’”); strCmd=strCmd->Concat(strCmd,strOrderStatus); strCmd=strCmd->Concat(strCmd,”’)”);

//Create a DataAdapter object and execute the command dataAdapter->UpdateCommand=new SqlCommand(NULL,sConn); dataAdapter->UpdateCommand->CommandText=strCmd; dataAdapter->UpdateCommand->ExecuteNonQuery();

}

catch(Exception *e)

{

USING COM+ SERVICES FROM .NET ASSEMBLIES Chapter 27 803

//Remove the following comment during debugging //Console::WriteLine(e->Message);

//If there was an error in the record insertion //cancel the entire operation and return an error.

ContextUtil::SetAbort();

return 1;

}

Next, update the Products table and set the ProdStatus of the product whose ID is passed as a parameter to Sold:

//Update the status of the product in product table to ‘sold’

SqlConnection *sConn2=new SqlConnection(); sConn2->set_ConnectionString(“Data Source=saik-d185;Initial Catalog=ArtShop;Integrated Security=SSPI”);

sConn2->Open();

SqlDataAdapter *dataAdapter2=new SqlDataAdapter();

try

{

//Construct the command string

strCmd=”Update Product set ProdStatus=’Sold’ where ProdID=’”; strCmd=strCmd->Concat(strCmd,strProdID); strCmd=strCmd->Concat(strCmd,”’”);

//Create the DataAdapter object and execute the query dataAdapter2->UpdateCommand=new SqlCommand(NULL,sConn2); dataAdapter2->UpdateCommand->CommandText=strCmd; dataAdapter2->UpdateCommand->ExecuteNonQuery();

//If no exceptions were raised till here commit the transaction.

ContextUtil::SetComplete();

}

catch(Exception *e)

{

//Console::WriteLine(e->Message);

//If there was an error rollback the transaction.

806 Project 8 .NET ASSEMBLIES WITH MANAGED C++ AND .NET

dim pObj

set pObj=CreateObject(“ProcessOrder.Class1”)

msgbox pObj.updateOrders( “2”,”2”,”222222”,”12/12/1990”,”Pending”)

Open the SQL Server Enterprise Manager and check the contents of the table Orders. The record should be added to it. If you want the transaction to fail, try calling the updateOrders method with an invalid value for ProdID.

Try changing the name of the table in the second part of the transaction (updating the Product table) to any invalid value. This way, the first insert command for the Orders table will succeed. However, the update command will fail. Since both the operations are a part of the same transaction, even the insert into the Orders table will be rolled back.

Summary

In this chapter, you created a .NET assembly that uses COM+ services to handle transactions. You saw that COM+ services plumbing is accessible to .NET applications and provides some useful functionality. MTS introduced component services that developers could use to provide transaction support, object pooling, declarative security, and other features to create enterprise applications. Windows 2000 COM+ services improved component services, introduced new features, and made it a part of the operating system. The EnterpriseServices namespace makes all of this accessible to .NET applications too.

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