Thread.ApartmentState Property

Definition

Namespace:

System.Threading

Assembly:

System.Threading.Thread.dll

Source:

Thread.CoreCLR.cs

Caution

The ApartmentState property has been deprecated. Use GetApartmentState, SetApartmentState or TrySetApartmentState instead.

Gets or sets the apartment state of this thread.

public:
 property System::Threading::ApartmentState ApartmentState { System::Threading::ApartmentState get(); void set(System::Threading::ApartmentState value); };

[System.Obsolete("The ApartmentState property has been deprecated. Use GetApartmentState, SetApartmentState or TrySetApartmentState instead.")]
public System.Threading.ApartmentState ApartmentState { get; set; }

[<System.Obsolete("The ApartmentState property has been deprecated. Use GetApartmentState, SetApartmentState or TrySetApartmentState instead.")>]
member this.ApartmentState : System.Threading.ApartmentState with get, set

Public Property ApartmentState As ApartmentState

Property Value

ApartmentState

One of the ApartmentState values. The initial value is Unknown.

Attributes

ObsoleteAttribute

Exceptions

ArgumentException

An attempt is made to set this property to a state that is not a valid apartment state (a state other than single-threaded apartment (STA) or multithreaded apartment (MTA)).

Examples

The following code example demonstrates how to set the apartment state of a thread.

using namespace System;
using namespace System::Threading;
ref class ApartmentTest
{
public:
   static void ThreadMethod()
   {
      Thread::Sleep( 1000 );
   }

};

int main()
{
   Thread^ newThread = gcnew Thread( gcnew ThreadStart( &ApartmentTest::ThreadMethod ) );
   newThread->SetApartmentState(ApartmentState::MTA);
   
   Console::WriteLine( "ThreadState: {0}, ApartmentState: {1}", newThread->ThreadState.ToString(), newThread->GetApartmentState().ToString() );
   newThread->Start();
   
   // Wait for newThread to start and go to sleep.
   Thread::Sleep( 300 );
   try
   {
      
      // This causes an exception since newThread is sleeping.
      newThread->SetApartmentState(ApartmentState::STA);
   }
   catch ( ThreadStateException^ stateException ) 
   {
      Console::WriteLine( "\n{0} caught:\n"
      "Thread is not in the Unstarted or Running state.", stateException->GetType()->Name );
      Console::WriteLine( "ThreadState: {0}, ApartmentState: {1}", newThread->ThreadState.ToString(), newThread->GetApartmentState().ToString() );
   }

}

using System;
using System.Threading;

class ApartmentTest
{
    static void Main()
    {
        Thread newThread = 
            new Thread(new ThreadStart(ThreadMethod));
        newThread.SetApartmentState(ApartmentState.MTA);

        Console.WriteLine("ThreadState: {0}, ApartmentState: {1}", 
            newThread.ThreadState, newThread.GetApartmentState());

        newThread.Start();

        // Wait for newThread to start and go to sleep.
        Thread.Sleep(300);
        try
        {
            // This causes an exception since newThread is sleeping.
            newThread.SetApartmentState(ApartmentState.STA);
        }
        catch(ThreadStateException stateException)
        {
            Console.WriteLine("\n{0} caught:\n" +
                "Thread is not in the Unstarted or Running state.", 
                stateException.GetType().Name);
            Console.WriteLine("ThreadState: {0}, ApartmentState: {1}",
                newThread.ThreadState, newThread.GetApartmentState());
        }
    }

    static void ThreadMethod()
    {
        Thread.Sleep(1000);
    }
}

open System.Threading

let threadMethod () = Thread.Sleep 1000

let newThread = Thread threadMethod
newThread.SetApartmentState ApartmentState.MTA

printfn $"ThreadState: {newThread.ThreadState}, ApartmentState: {newThread.GetApartmentState()}"

newThread.Start()

// Wait for newThread to start and go to sleep.
Thread.Sleep 300

try
    // This causes an exception since newThread is sleeping.
    newThread.SetApartmentState ApartmentState.STA

with :? ThreadStateException as stateException ->
    printfn $"\n{stateException.GetType().Name} caught:\nThread is not in the Unstarted or Running state."
    printfn $"ThreadState: {newThread.ThreadState}, ApartmentState: {newThread.GetApartmentState()}"

Imports System.Threading

Public Class ApartmentTest

    <MTAThread> _
    Shared Sub Main()
    
        Dim newThread As Thread = New Thread(AddressOf ThreadMethod)
        newThread.SetApartmentState(ApartmentState.MTA)

        Console.WriteLine("ThreadState: {0}, ApartmentState: {1}", _
            newThread.ThreadState, newThread.GetApartmentState())

        newThread.Start()

        ' Wait for newThread to start and go to sleep.
        Thread.Sleep(300)
        Try
            ' This causes an exception since newThread is sleeping.
            newThread.SetApartmentState(ApartmentState.STA)
        Catch stateException As ThreadStateException
            Console.WriteLine(vbCrLf & "{0} caught:" & vbCrLf & _
                "Thread is not In the Unstarted or Running state.", _
                stateException.GetType().Name)
            Console.WriteLine("ThreadState: {0}, ApartmentState: " & _
                "{1}", newThread.ThreadState, newThread.GetApartmentState())
        End Try

    End Sub

    Shared Sub ThreadMethod()
        Thread.Sleep(1000)
    End Sub

End Class

Remarks

The ApartmentState property is obsolete. The non-obsolete alternatives are the GetApartmentState method to retrieve the apartment state and the SetApartmentState method to set the apartment state.

In .NET Framework versions 1.0 and 1.1, the ApartmentState property marks a thread to indicate that it will execute in a single-threaded or multithreaded apartment. This property can be set when the thread is in the Unstarted or Running thread state; however, it can be set only once for a thread. If the property has not been set, it returns Unknown.

An attempt to use the ApartmentState property to set the apartment state of a thread whose apartment state has already been set is ignored. However, the SetApartmentState method throws a InvalidOperationException in this case.

Important

In .NET Framework version 2.0, new threads are initialized as ApartmentState.MTA if their apartment state has not been set before they are started. The main application thread is initialized to ApartmentState.MTA by default. You can no longer set the main application thread to ApartmentState.STA by setting the System.Threading.ApartmentState property on the first line of code. Use the STAThreadAttribute instead.

In .NET Framework version 2.0, you can specify the COM threading model for a C++ application using the /CLRTHREADATTRIBUTE (Set CLR Thread Attribute) linker option.

See also

• ThreadState
• GetApartmentState()
• SetApartmentState(ApartmentState)