Which are ways to run C# Application in Single Thread Apartment [STA]?

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Hello,

I have one C# Window Services based application in which using ActiveX which required to be run on Single thread apartment [STA]. That ActiveX doing TCP communication.

If I run it as MTA then it gives exception "ActiveX control cannot be instantiated because the current thread is not in a single-threaded apartment."

Now I found two ways to run it in STA.

1) Write [STAThread] in entry level method of application. Like below:

C#

[STAThread]
static void Main()

2) Start New thread and set apartment state to STA like below

C#

Thread t = new Thread(() => StartTCPCommunication());
t.SetApartmentState(ApartmentState.STA);
t.Start();

Now my question is what is the difference between above 2 ways.

Because my application structure is like that I can't use Way#1 becuase my appication running as Windows Service. so even if I use way#1 it give me ActiveX exception mentioned above.

If I convert windows services to Windows Desktop application then same code working fine with Way#1

But I need windows service so I need to use Way#2, but when I used that I can not do TCP communication and even not get any exception.

So can any one help me to figure out the issue ? or some alternate way ?

Thanks in advance

Posted 14-Apr-15 0:31am

npdev13

Updated 14-Apr-15 0:32am

v2

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Sergey Alexandrovich Kryukov 14-Apr-15 10:24am

First of all, why do you think you need STA for your service? Yes, it's possible that you need it; I just want to know why.
—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2015-04-14T04:41:00

First of all, here is the simplest advice: don't use any stupid and obsolete ActiveX controls for TCP communications. Just listen how it sounds: ActiveX? In .NET? Seriously?

Instead, you can use the sockets, or, even better and simpler, the class System.Net.Sockets.TcpListener. which is also the part of sockets API, wrapped for your convenience:
https://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener%28v=vs.110%29.aspx,
https://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener%28v=vs.110%29.aspx.

Also, I don't know why you decided that Way#1 cannot be used for a service. A service application also has the entry point method, so you can apply the attribute [System.STAThread] to it.

And of course you always could use Way#2. You did not provide any information on why it did not work, but you could face different problems by different reasons. For example, you could create this STAThread but still do something problematic not in this thread, but in some other thread. :-)

—SA