Sets the apartment state of a thread before it is started.
Assembly: mscorlib (in mscorlib.dll)
[<HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, SelfAffectingThreading = true)>] member TrySetApartmentState : state:ApartmentState -> bool
- Type: System.Threading.ApartmentState
The new apartment state.
Return ValueType: System.Boolean
true if the apartment state is set; otherwise, false.
New threads are initialized as ApartmentState.MTA if their apartment state has not been set before they are started. Apartment state must be set before a thread is started.
The main application thread is initialized to ApartmentState.MTA by default. The only way to set the apartment state of the main application thread to ApartmentState.STA is to apply the STAThreadAttribute attribute to the entry point method.
The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: Synchronization | SelfAffectingThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.
The following code example demonstrates the GetApartmentState, SetApartmentState, and methods. The code example creates a thread. Before the thread is started, GetApartmentState displays the initial ApartmentState.Unknown state and SetApartmentState changes the state to ApartmentState.STA. The method then returns false when attempting to change the state to ApartmentState.MTA because the apartment state is already set. If the same operation had been attempted with SetApartmentState, InvalidOperationException would have been thrown.
After the thread is started, the method is used again. This time it throws ThreadStateException because the thread has already been started.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.