COM+ Integration: How .NET Enterprise Services Can Help You Build Distributed Applications

A Quick Review of COM+

Implementing COM+ Configured Classes with the CLR

  using System.EnterpriseServices;
namespace ESExample
{
  public class MyCfgClass : ServicedComponent
  {
    public MyCfgClass() {}
    •••
  }
}

Declarative Attributes

  using System.EnterpriseServices;
namespace ESExample
{
  [ Transaction(TransactionOption.Required) ]
  public class MyTxCfgClass : ServicedComponent
  {
    public MyTxCfgClass() {}
    •••
  }
}

  using System.EnterpriseServices;
[assembly: ApplicationName("MyApp")]
[assembly: ApplicationActivation(ActivationOption.Library)]
namespace ESExample
{
  [ Transaction(TransactionOption.Required) ]
  public class MyTxCfgClass : ServicedComponent
  {
    public MyTxCfgClass() {}
    •••
  }
}

Implementing IObjectConstruct and IObjectControl

  namespace ESExample
{
  [ ObjectPooling(true, 5, 20) ]
  public class MyPooledCfgClass : ServicedComponent
  {
    public MyPooledCfgClass() {}
    // override CanBePooled so that instances can be
    // reused, use default implementations of Activate
    // and Deactivate provided by ServicedComponent
    public override bool CanBePooled() { return true; }
  }
}

ContextUtil and SecurityCallContext

Compiling a Configured Class

  using System.EnterpriseServices;
using System.Reflection;
[assembly: ApplicationName("MyApp")]
[assembly: ApplicationActivation(ActivationOption.Library)]
// AssemblyKeyFile attribute references keyfile generated
// by sn.exe - assembly will have strong name
[assembly: AssemblyKeyFile("keyfile")]
namespace ESExample
{
•••
}

  sn -k keyfile
csc /out:ESExample.dll /t:library
    /r:System.EnterpriseServices.dll MyCfgClass.cs

Deploying a Configured Class

  regsvcs ESExample.dll

  // all these attributes
// are compatible
[ Transaction(TransactionOption.Required) ]
[ Synchronization(SynchronizationOption.Required) ]
[ JustInTimeActivation(true) ]
public class MyTxCfgClass : ServicedComponent
{
  public MyTxCfgClass() {}
  •••
}

  gacutil -i ESExample.dll

Implementing a Client

  using ESExample;
public class Client
{
  public static void Main(string[] args)
  {
    MyTxCfgClass tcc = new MyTxCfgClass();
    ... // use object as desired
  }
}

  csc /r:ESExample.dll Client.cs

Subtle Complexities

Static Methods and Properties

Managing Precious Resources

  public void UseADatabase(void)
{
  System.Data.SqlClient.SqlConnection =
      new System.Data.SqlClient.SqlConnection(...);
    ... // use connection to execute statements
}

  public void UseADatabase(void)
{
  System.Data.SqlClient.SqlConnection conn =
      new System.Data.SqlClient.SqlConnection(...);
  ... // use connection to execute statements
  conn = null;
  System.GC.Collect();    
}

  public void UseADatabase(void)
{
  System.Data.SqlClient.SqlConnection conn =
      new System.Data.SqlClient.SqlConnection(...);
  try
  {
    ... // use connection to execute statements
  }
  finally
  {
    conn.Dispose();
  }
}

  public void UseAPooledObject(void)
{
  MyPooledCfgClass pcc = new MyPooledCfgClass();
  try
  {
    ... // use pooled object to do something
  }
  finally
  {
    pcc.Dispose();
  }
}

  [ Synchronization(SynchronizedOption.Required) ]
public class MyCfgClass : ServicedComponent
{
  public new void Dispose()
  {
    ... // do whatever
    base.Dispose(); // call base to clean up
  }
}

The Future