Calling STA COM component from WCF.

Question

Hi,

 

I have a VB STA com component and I use it as follows

 

public class Service1 : IService1

{

        private ProjectSTA.ClassSTA x; ‘VB6 STA Component

 

        public string GetData(int value)

        {

         Console.Write(Thread.CurrentThread.GetApartmentState().ToString()); 'return MTA

            return x.GetName();

 

       }

}

 

public CompositeType GetDataUsingDataContract(CompositeType composite)

{

            x = new ProjectSTA.ClassSTA();

}

        

 

 

Reading many articles I was expecting that it will fail since the service is run under MTA?!

I am using VS.NET 2010

Thanks in advance

Answer 1

Looks like the STA component is created in a different thread(the default thread created by com?)

Tomer

Answer 2

I think i understand....

.NET will correctly marshal calls from MTA to STA, the problem is that If several COM components is used by the

Service all calls to ALL components will be serialized through a single thread

So all parallelism is lost.

 

Can any one confirm this?

Answer 3

When WCF calls a com object it effectivey blocks all other calls to the WCF service until that com call completes, effectively becoming single threaded! 

Even though WCF is MTA the MTA threads have to wait till the STA com call completes.One option is to expose COM+ component as a WCF service ,so we can use this option to communicate with COM+ component.

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