Thread.Start Method

Definition

Namespace:

System.Threading

Assembly:

System.Threading.Thread.dll

Causes a thread to be scheduled for execution.

Overloads

Start()	Causes the operating system to change the state of the current instance to Running.
Start(Object)	Causes the operating system to change the state of the current instance to Running, and optionally supplies an object containing data to be used by the method the thread executes.

Start()

Source:

Thread.cs

Causes the operating system to change the state of the current instance to Running.

public:
 void Start();

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public void Start ();

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.Start : unit -> unit

Public Sub Start ()

Attributes

UnsupportedOSPlatformAttribute

Exceptions

ThreadStateException

The thread has already been started.

OutOfMemoryException

There is not enough memory available to start this thread.

Examples

The following example creates and starts a thread.

using namespace System;
using namespace System::Threading;

public ref class ThreadWork
{
public:
   static void DoWork()
   {
      for ( int i = 0; i < 3; i++ )
      {
         Console::WriteLine( "Working thread..." );
         Thread::Sleep( 100 );
      }
   }
};

int main()
{
   ThreadStart^ myThreadDelegate = gcnew ThreadStart(&ThreadWork::DoWork);
   Thread^ thread1 = gcnew Thread( myThreadDelegate );
   thread1->Start();
   for ( int i = 0; i < 3; i++ )
   {
      Console::WriteLine( "In main." );
      Thread::Sleep( 100 );
   }
}
// The example displays output like the following:
//       In main.
//       Working thread...
//       In main.
//       Working thread...
//       In main.
//       Working thread...

using System;
using System.Threading;

public class ThreadWork
{
   public static void DoWork()
   {
      for(int i = 0; i<3;i++) {
         Console.WriteLine("Working thread...");
         Thread.Sleep(100);
      }
   }
}
class ThreadTest
{
   public static void Main()
   {
      Thread thread1 = new Thread(ThreadWork.DoWork);
      thread1.Start();
      for (int i = 0; i<3; i++) {
         Console.WriteLine("In main.");
         Thread.Sleep(100);
      }
   }
}
// The example displays output like the following:
//       In main.
//       Working thread...
//       In main.
//       Working thread...
//       In main.
//       Working thread...

open System.Threading

module ThreadWork = 
    let doWork () =
        for _ = 0 to 2 do 
            printfn "Working thread..."
            Thread.Sleep 100

let thread1 = Thread ThreadWork.doWork
thread1.Start()
for _ = 0 to 2 do 
    printfn "In main."
    Thread.Sleep 100

// The example displays output like the following:
//       In main.
//       Working thread...
//       In main.
//       Working thread...
//       In main.
//       Working thread...

Imports System.Threading

Public Class ThreadWork
   Public Shared Sub DoWork()
      Dim i As Integer
      For i = 0 To 2
         Console.WriteLine("Working thread...")
         Thread.Sleep(100)
      Next i
   End Sub
End Class

Class ThreadTest
   Public Shared Sub Main()
      Dim thread1 As New Thread(AddressOf ThreadWork.DoWork)
      thread1.Start()
      Dim i As Integer
      For i = 0 To 2
         Console.WriteLine("In main.")
         Thread.Sleep(100)
      Next
   End Sub
End Class
' The example displays output like the following:
'       In main.
'       Working thread...
'       In main.
'       Working thread...
'       In main.
'       Working thread...

Remarks

Once a thread is in the ThreadState.Running state, the operating system can schedule it for execution. The thread begins executing at the first line of the method represented by the ThreadStart or ParameterizedThreadStart delegate supplied to the thread constructor. Note that the call to Start does not block the calling thread.

Note

If this overload is used with a thread created using a ParameterizedThreadStart delegate, null is passed to the method executed by the thread.

Once the thread terminates, it cannot be restarted with another call to Start.

See also

• Threads and Threading
• Creating Threads and Passing Data at Start Time

Start(Object)

Source:

Thread.cs

Causes the operating system to change the state of the current instance to Running, and optionally supplies an object containing data to be used by the method the thread executes.

public:
 void Start(System::Object ^ parameter);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public void Start (object? parameter);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.Start : obj -> unit

Public Sub Start (parameter As Object)

Parameters

parameter

Object

An object that contains data to be used by the method the thread executes.

Attributes

UnsupportedOSPlatformAttribute

Exceptions

ThreadStateException

The thread has already been started.

OutOfMemoryException

There is not enough memory available to start this thread.

InvalidOperationException

This thread was created using a ThreadStart delegate instead of a ParameterizedThreadStart delegate.

Examples

The following example creates a ParameterizedThreadStart delegate with a static method and an instance method.

using namespace System;
using namespace System::Threading;

namespace SystemThreadingExample
{
    public ref class Work
    {
    public:
        void StartThreads()
        {
            // Start a thread that calls a parameterized static method.
            Thread^ newThread = gcnew
                Thread(gcnew ParameterizedThreadStart(Work::DoWork));
            newThread->Start(42);
              
            // Start a thread that calls a parameterized instance method.
            Work^ someWork = gcnew Work;
            newThread = gcnew Thread(
                        gcnew ParameterizedThreadStart(someWork,
                        &Work::DoMoreWork));
            newThread->Start("The answer.");
        }

        static void DoWork(Object^ data)
        {
            Console::WriteLine("Static thread procedure. Data='{0}'", 
                data);
        }

        void DoMoreWork(Object^ data)
        {
            Console::WriteLine("Instance thread procedure. Data='{0}'", 
                data);
        }
    };
}

//Entry point of example application
int main()
{
    SystemThreadingExample::Work^ samplework = 
        gcnew SystemThreadingExample::Work();
    samplework->StartThreads();
}
// This example displays output like the following:
//       Static thread procedure. Data='42'
//       Instance thread procedure. Data='The answer.'

using System;
using System.Threading;

public class Work
{
    public static void Main()
    {
        // Start a thread that calls a parameterized static method.
        Thread newThread = new Thread(Work.DoWork);
        newThread.Start(42);

        // Start a thread that calls a parameterized instance method.
        Work w = new Work();
        newThread = new Thread(w.DoMoreWork);
        newThread.Start("The answer.");
    }
 
    public static void DoWork(object data)
    {
        Console.WriteLine("Static thread procedure. Data='{0}'",
            data);
    }

    public void DoMoreWork(object data)
    {
        Console.WriteLine("Instance thread procedure. Data='{0}'",
            data);
    }
}
// This example displays output like the following:
//       Static thread procedure. Data='42'
//       Instance thread procedure. Data='The answer.'

open System.Threading

type Work() =
    static member DoWork(data: obj) =
        printfn $"Static thread procedure. Data='{data}'"

    member _.DoMoreWork(data: obj) =
        printfn $"Instance thread procedure. Data='{data}'"

// Start a thread that calls a parameterized static method.
let newThread = Thread(ParameterizedThreadStart Work.DoWork)
newThread.Start 42

// Start a thread that calls a parameterized instance method.
let w = Work()
let newThread2 = Thread(ParameterizedThreadStart w.DoMoreWork)
newThread.Start "The answer."

// This example displays output like the following:
//       Static thread procedure. Data='42'
//       Instance thread procedure. Data='The answer.'

Imports System.Threading

Public Class Work
    Shared Sub Main()
        ' Start a thread that calls a parameterized static method.
        Dim newThread As New Thread(AddressOf Work.DoWork)
        newThread.Start(42)

        ' Start a thread that calls a parameterized instance method.
        Dim w As New Work()
        newThread = New Thread(AddressOf w.DoMoreWork)
        newThread.Start("The answer.")
    End Sub
 
    Public Shared Sub DoWork(ByVal data As Object)
        Console.WriteLine("Static thread procedure. Data='{0}'",
                          data)
    End Sub

    Public Sub DoMoreWork(ByVal data As Object) 
        Console.WriteLine("Instance thread procedure. Data='{0}'",
                          data)
    End Sub
End Class
' This example displays output like the following:
'    Static thread procedure. Data='42'
'    Instance thread procedure. Data='The answer.'

Remarks

Once a thread is in the ThreadState.Running state, the operating system can schedule it for execution. The thread begins executing at the first line of the method represented by the ThreadStart or ParameterizedThreadStart delegate supplied to the thread constructor. Note that the call to Start does not block the calling thread.

Once the thread terminates, it cannot be restarted with another call to Start.

This overload and the ParameterizedThreadStart delegate make it easy to pass data to a thread procedure, but the technique is not type safe because any object can be passed to this overload. A more robust way to pass data to a thread procedure is to put both the thread procedure and the data fields into a worker object. For more information, see Creating Threads and Passing Data at Start Time.

See also

• ParameterizedThreadStart
• AppDomain
• Creating Threads