Indicates that the COM threading model for an application is multithreaded apartment (MTA).
[System.AttributeUsage(System.AttributeTargets.Method)] [System.Runtime.InteropServices.ComVisible(true)] public sealed class MTAThreadAttribute : Attribute
Apply this attribute to the entry point method (the
Main() method in C# and Visual Basic). It has no effect on other methods. To set the apartment state of threads you start in your code, use the Thread.SetApartmentState or Thread.TrySetApartmentState method before starting the thread.
For an overview of COM threading models, see Understanding and Using COM Threading Models.
COM threading models only apply to applications that use COM interop. The COM threading model can be set to single-threaded apartment or multithreaded apartment. The application thread is only initialized for COM interop if the thread actually makes a call to a COM component. If COM interop is not used, then the thread is not initialized, and the MTAThreadAttribute attribute, if it is present, has no effect.
Starting with the .NET Framework version 2.0, the default threading model for COM interop depends on the language in which you are developing your application, as the following table shows.
|Language||COM apartment model|
|Visual Basic||Single-threaded apartment|
To change these defaults, you use the MTAThreadAttribute attribute to set the threading model for the application, or call the Thread.SetApartmentState or Thread.TrySetApartmentState method before starting the thread to set the threading model for a particular thread. In C++, you can also use the /CLRTHREADATTRIBUTE (Set CLR Thread Attribute) linker option to specify the apartment model.
Some of the cases in which you want to use the MTAThreadAttribute attribute to explicitly set the threading model to multithreaded apartment include the following:
You're developing a Visual Basic app that calls to a C# library that in turn relies on COM interop. Because the multithreaded apartment model is the default for C#, you should change your app's threading model to multithreaded by using the MTAThreadAttribute attribute.
Your application makes calls to COM components that use the multithreaded apartment model.
Initializes a new instance of the MTAThreadAttribute class.
|TypeId||Inherited from Attribute|