Task.Delay Method

Reference

Definition

Namespace:: System.Threading.Tasks

Assembly:: System.Threading.Tasks.dll

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Creates a task that will complete after a time delay.

Overloads

Delay(Int32)	Creates a task that completes after a specified number of milliseconds.
Delay(TimeSpan)	Creates a task that completes after a specified time interval.
Delay(Int32, CancellationToken)	Creates a cancellable task that completes after a specified number of milliseconds.
Delay(TimeSpan, CancellationToken)	Creates a cancellable task that completes after a specified time interval.
Delay(TimeSpan, TimeProvider)	Creates a task that completes after a specified time interval.
Delay(TimeSpan, TimeProvider, CancellationToken)	Creates a cancellable task that completes after a specified time interval.

Delay(Int32)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Creates a task that completes after a specified number of milliseconds.

public:
 static System::Threading::Tasks::Task ^ Delay(int millisecondsDelay);

public static System.Threading.Tasks.Task Delay (int millisecondsDelay);

static member Delay : int -> System.Threading.Tasks.Task

Public Shared Function Delay (millisecondsDelay As Integer) As Task

Parameters

millisecondsDelay: Int32

The number of milliseconds to wait before completing the returned task, or -1 to wait indefinitely.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

The millisecondsDelay argument is less than -1.

Examples

The following example shows a simple use of the Delay method.

using System;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var t = Task.Run(async delegate
              {
                 await Task.Delay(1000);
                 return 42;
              });
      t.Wait();
      Console.WriteLine("Task t Status: {0}, Result: {1}",
                        t.Status, t.Result);
   }
}
// The example displays the following output:
//        Task t Status: RanToCompletion, Result: 42

open System.Threading.Tasks

let t =
    Task.Run<int>(fun () ->
        task {
            do! Task.Delay 1000
            return 42
        })

t.Wait()
printfn $"Task t Status: {t.Status}, Result: {t.Result}"

// The example displays the following output:
//        Task t Status: RanToCompletion, Result: 42

Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim t = Task.Run(Async Function()
                                Await Task.Delay(1000)
                                Return 42
                       End Function)
      t.Wait()
      Console.WriteLine("Task t Status: {0}, Result: {1}",
                        t.Status, t.Result)
   End Sub
End Module
' The example displays the following output:
'       Task t Status: RanToCompletion, Result: 42

Remarks

The Delay method is typically used to delay the operation of all or part of a task for a specified time interval. Most commonly, the time delay is introduced:

At the beginning of the task, as the following example shows.

Stopwatch sw = Stopwatch.StartNew();
var delay = Task.Delay(1000).ContinueWith(_ =>
                           { sw.Stop();
                             return sw.ElapsedMilliseconds; } );

Console.WriteLine("Elapsed milliseconds: {0}", delay.Result);
// The example displays output like the following:
//        Elapsed milliseconds: 1013

    let sw = Stopwatch.StartNew()

    let delay =
        Task
            .Delay(1000)
            .ContinueWith(fun _ ->
                sw.Stop()
                sw.ElapsedMilliseconds)

    printfn $"Elapsed milliseconds: {delay.Result}"
// The example displays output like the following:
//        Elapsed milliseconds: 1013

Dim sw As Stopwatch = Stopwatch.StartNew()
Dim delay1 = Task.Delay(1000)
Dim delay2 = delay1.ContinueWith( Function(antecedent)
                        sw.Stop()
                        Return sw.ElapsedMilliseconds
                      End Function)

Console.WriteLine("Elapsed milliseconds: {0}", delay2.Result)
' The example displays output like the following:
'        Elapsed milliseconds: 1013

Sometime while the task is executing. In this case, the call to the Delay method executes as a child task within a task, as the following example shows. Note that since the task that calls the Delay method executes asynchronously, the parent task must wait for it to complete by using the await keyword.

var delay = Task.Run( async () => { Stopwatch sw = Stopwatch.StartNew();
                                    await Task.Delay(2500);
                                    sw.Stop();
                                    return sw.ElapsedMilliseconds; });

Console.WriteLine("Elapsed milliseconds: {0}", delay.Result);
// The example displays output like the following:
//        Elapsed milliseconds: 2501

    let delay =
        Task.Run<int64>(fun () ->
            task {
                let sw = Stopwatch.StartNew()
                do! Task.Delay 2500
                sw.Stop()
                return sw.ElapsedMilliseconds
            })

    printfn $"Elapsed milliseconds: {delay.Result}"
// The example displays output like the following:
//        Elapsed milliseconds: 2501

Dim delay = Task.Run( Async Function()
                         Dim sw As Stopwatch = Stopwatch.StartNew()
                         Await Task.Delay(2500)
                         sw.Stop()
                         Return sw.ElapsedMilliseconds
                      End Function )

Console.WriteLine("Elapsed milliseconds: {0}", delay.Result)
' The example displays output like the following:
'        Elapsed milliseconds: 2501

After the specified time delay, the task is completed in the RanToCompletion state.

This method depends on the system clock. This means that the time delay will approximately equal the resolution of the system clock if the millisecondsDelay argument is less than the resolution of the system clock, which is approximately 15 milliseconds on Windows systems.

Note

The system clock that is used is the same clock used by GetTickCount, which is not affected by changes made with timeBeginPeriod and timeEndPeriod.

Applies to

Delay(TimeSpan)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Creates a task that completes after a specified time interval.

public:
 static System::Threading::Tasks::Task ^ Delay(TimeSpan delay);

public static System.Threading.Tasks.Task Delay (TimeSpan delay);

static member Delay : TimeSpan -> System.Threading.Tasks.Task

Public Shared Function Delay (delay As TimeSpan) As Task

Parameters

delay: TimeSpan

The time span to wait before completing the returned task, or Timeout.InfiniteTimeSpan to wait indefinitely.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

delay represents a negative time interval other than Timeout.InfiniteTimeSpan.

-or-

The delay argument's TotalMilliseconds property is greater than 4294967294 on .NET 6 and later versions, or Int32.MaxValue on all previous versions.

Examples

The following example shows a simple use of the Delay method.

using System;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var t = Task.Run(async delegate
              {
                 await Task.Delay(TimeSpan.FromSeconds(1.5));
                 return 42;
              });
      t.Wait();
      Console.WriteLine("Task t Status: {0}, Result: {1}",
                        t.Status, t.Result);
   }
}
// The example displays the following output:
//        Task t Status: RanToCompletion, Result: 42

open System
open System.Threading.Tasks

let t =
    Task.Run<int>(fun () ->
        task {
            do! Task.Delay(TimeSpan.FromSeconds 1.5)
            return 42
        })

t.Wait()
printfn $"Task t Status: {t.Status}, Result: {t.Result}"

// The example displays the following output:
//        Task t Status: RanToCompletion, Result: 42

Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim t = Task.Run(Async Function()
                                Await Task.Delay(TimeSpan.FromSeconds(1.5))
                                Return 42
                       End Function)
      t.Wait()
      Console.WriteLine("Task t Status: {0}, Result: {1}",
                        t.Status, t.Result)
   End Sub
End Module
' The example displays the following output:
'       Task t Status: RanToCompletion, Result: 42

Remarks

After the specified time delay, the task is completed in RanToCompletion state.

For usage scenarios and additional examples, see the documentation for the Delay(Int32) overload.

This method depends on the system clock. This means that the time delay will approximately equal the resolution of the system clock if the delay argument is less than the resolution of the system clock, which is approximately 15 milliseconds on Windows systems.

Note

The system clock that is used is the same clock used by GetTickCount, which is not affected by changes made with timeBeginPeriod and timeEndPeriod.

Applies to

Delay(Int32, CancellationToken)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Creates a cancellable task that completes after a specified number of milliseconds.

public:
 static System::Threading::Tasks::Task ^ Delay(int millisecondsDelay, System::Threading::CancellationToken cancellationToken);

public static System.Threading.Tasks.Task Delay (int millisecondsDelay, System.Threading.CancellationToken cancellationToken);

static member Delay : int * System.Threading.CancellationToken -> System.Threading.Tasks.Task

Public Shared Function Delay (millisecondsDelay As Integer, cancellationToken As CancellationToken) As Task

Parameters

millisecondsDelay: Int32

The number of milliseconds to wait before completing the returned task, or -1 to wait indefinitely.

cancellationToken: CancellationToken

A cancellation token to observe while waiting for the task to complete.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

The millisecondsDelay argument is less than -1.

OperationCanceledException

The task has been canceled. This exception is stored into the returned task.

ObjectDisposedException

The provided cancellationToken has already been disposed.

TaskCanceledException

The task has been canceled.

Examples

The following example launches a task that includes a call to the Delay(Int32, CancellationToken) method with a one second delay. Before the delay interval elapses, the token is cancelled. The output from the example shows that, as a result, a TaskCanceledException is thrown, and the tasks' Status property is set to Canceled.

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      CancellationTokenSource source = new CancellationTokenSource();

      var t = Task.Run(async delegate
              {
                 await Task.Delay(1000, source.Token);
                 return 42;
              });
      source.Cancel();
      try {
         t.Wait();
      }
      catch (AggregateException ae) {
         foreach (var e in ae.InnerExceptions)
            Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message);
      }
      Console.Write("Task t Status: {0}", t.Status);
      if (t.Status == TaskStatus.RanToCompletion)
         Console.Write(", Result: {0}", t.Result);
      source.Dispose();
   }
}
// The example displays the following output:
//       TaskCanceledException: A task was canceled.
//       Task t Status: Canceled

open System
open System.Threading
open System.Threading.Tasks

let source = new CancellationTokenSource()

let t =
    Task.Run<int>(fun () ->
        task {
            do! Task.Delay(1000, source.Token)
            return 42
        })

source.Cancel()

try
    t.Wait()

with :? AggregateException as ae ->
    for e in ae.InnerExceptions do
        printfn $"{e.GetType().Name}: {e.Message}"

printf $"Task t Status: {t.Status}"

if t.Status = TaskStatus.RanToCompletion then
    printf $", Result: {t.Result}"

source.Dispose()


// The example displays the following output:
//       TaskCanceledException: A task was canceled.
//       Task t Status: Canceled

Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim source As New CancellationTokenSource()
      
      Dim t = Task.Run(Async Function()
                                Await Task.Delay(1000, source.Token)
                                Return 42
                       End Function)
      source.Cancel()
      Try
         t.Wait()
      Catch ae As AggregateException
         For Each e In ae.InnerExceptions
            Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message)
         Next
      End Try
      Console.Write("Task t Status: {0}", t.Status)
      If t.Status = TaskStatus.RanToCompletion Then
         Console.Write(", Result: {0}", t.Result)
      End If
      source.Dispose()
   End Sub
End Module
' The example displays the following output:
'       TaskCanceledException: A task was canceled.
'       Task t Status: Canceled

Remarks

If the cancellation token is signaled before the specified time delay, a TaskCanceledException exception results, and the task is completed in the Canceled state. Otherwise, the task is completed in the RanToCompletion state once the specified time delay has elapsed.

For usage scenarios and additional examples, see the documentation for the Delay(Int32) overload.

Note

The system clock that is used is the same clock used by GetTickCount, which is not affected by changes made with timeBeginPeriod and timeEndPeriod.

Applies to

Delay(TimeSpan, CancellationToken)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Creates a cancellable task that completes after a specified time interval.

public:
 static System::Threading::Tasks::Task ^ Delay(TimeSpan delay, System::Threading::CancellationToken cancellationToken);

public static System.Threading.Tasks.Task Delay (TimeSpan delay, System.Threading.CancellationToken cancellationToken);

static member Delay : TimeSpan * System.Threading.CancellationToken -> System.Threading.Tasks.Task

Public Shared Function Delay (delay As TimeSpan, cancellationToken As CancellationToken) As Task

Parameters

delay: TimeSpan

The time span to wait before completing the returned task, or Timeout.InfiniteTimeSpan to wait indefinitely.

cancellationToken: CancellationToken

A cancellation token to observe while waiting for the task to complete.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

delay represents a negative time interval other than Timeout.InfiniteTimeSpan.

-or-

The delay argument's TotalMilliseconds property is greater than 4294967294 on .NET 6 and later versions, or Int32.MaxValue on all previous versions.

OperationCanceledException

The task has been canceled. This exception is stored into the returned task.

ObjectDisposedException

The provided cancellationToken has already been disposed.

TaskCanceledException

The task has been canceled.

Examples

The following example launches a task that includes a call to the Delay(TimeSpan, CancellationToken) method with a 1.5 second delay. Before the delay interval elapses, the token is cancelled. The output from the example shows that, as a result, a TaskCanceledException is thrown, and the tasks' Status property is set to Canceled.

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      CancellationTokenSource source = new CancellationTokenSource();

      var t = Task.Run(async delegate
              {
                 await Task.Delay(TimeSpan.FromSeconds(1.5), source.Token);
                 return 42;
              });
      source.Cancel();
      try {
         t.Wait();
      }
      catch (AggregateException ae) {
         foreach (var e in ae.InnerExceptions)
            Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message);
      }
      Console.Write("Task t Status: {0}", t.Status);
      if (t.Status == TaskStatus.RanToCompletion)
         Console.Write(", Result: {0}", t.Result);
      source.Dispose();
   }
}
// The example displays output like the following:
//       TaskCanceledException: A task was canceled.
//       Task t Status: Canceled

open System
open System.Threading
open System.Threading.Tasks

let source = new CancellationTokenSource()

let t =
    Task.Run<int>(fun () ->
        task {

            do! Task.Delay(TimeSpan.FromSeconds(1.5), source.Token)
            return 42
        })

source.Cancel()

try
    t.Wait()

with :? AggregateException as ae ->
    for e in ae.InnerExceptions do
        printfn $"{e.GetType().Name}: {e.Message}"

printf $"Task t Status: {t.Status}"

if t.Status = TaskStatus.RanToCompletion then
    printf $", Result: {t.Result}"

source.Dispose()

// The example displays output like the following:
//       TaskCanceledException: A task was canceled.
//       Task t Status: Canceled

Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim source As New CancellationTokenSource()
      
      Dim t = Task.Run(Async Function()
                                Await Task.Delay(TimeSpan.FromSeconds(1.5),
                                                 source.Token)
                                Return 42
                       End Function)
      source.Cancel()
      Try
         t.Wait()
      Catch ae As AggregateException
         For Each e In ae.InnerExceptions
            Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message)
         Next
      End Try
      Console.Write("Task t Status: {0}", t.Status)
      If t.Status = TaskStatus.RanToCompletion Then
         Console.Write(", Result: {0}", t.Result)
      End If
      source.Dispose()
   End Sub
End Module
' The example displays output like the following:
'       TaskCanceledException: A task was canceled.
'       Task t Status: Canceled

Note that this example includes a potential race condition: it depends on the task asynchronously executing the delay when the token is cancelled. Although the 1.5 second delay from the call to the Delay(TimeSpan, CancellationToken) method makes that assumption likely, it is nevertheless possible that the call to the Delay(TimeSpan, CancellationToken) method could return before the token is cancelled. In that case, the example produces the following output:

Task t Status: RanToCompletion, Result: 42

Remarks

For usage scenarios and additional examples, see the documentation for the Delay(Int32) overload.

Note

The system clock that is used is the same clock used by GetTickCount, which is not affected by changes made with timeBeginPeriod and timeEndPeriod.

Applies to

Delay(TimeSpan, TimeProvider)

Source:: Task.cs

Source:: Task.cs

Creates a task that completes after a specified time interval.

public:
 static System::Threading::Tasks::Task ^ Delay(TimeSpan delay, TimeProvider ^ timeProvider);

public static System.Threading.Tasks.Task Delay (TimeSpan delay, TimeProvider timeProvider);

static member Delay : TimeSpan * TimeProvider -> System.Threading.Tasks.Task

Public Shared Function Delay (delay As TimeSpan, timeProvider As TimeProvider) As Task

Parameters

delay: TimeSpan

The TimeSpan to wait before completing the returned task, or InfiniteTimeSpan to wait indefinitely.

timeProvider: TimeProvider

The TimeProvider with which to interpret delay.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

delay represents a negative time interval other than InfiniteTimeSpan.

-or-

delay's TotalMilliseconds property is greater than 4294967294.

ArgumentNullException

The timeProvider argument is null.

Applies to

Delay(TimeSpan, TimeProvider, CancellationToken)

Source:: Task.cs

Source:: Task.cs

Creates a cancellable task that completes after a specified time interval.

public:
 static System::Threading::Tasks::Task ^ Delay(TimeSpan delay, TimeProvider ^ timeProvider, System::Threading::CancellationToken cancellationToken);

public static System.Threading.Tasks.Task Delay (TimeSpan delay, TimeProvider timeProvider, System.Threading.CancellationToken cancellationToken);

static member Delay : TimeSpan * TimeProvider * System.Threading.CancellationToken -> System.Threading.Tasks.Task

Public Shared Function Delay (delay As TimeSpan, timeProvider As TimeProvider, cancellationToken As CancellationToken) As Task

Parameters

delay: TimeSpan

The TimeSpan to wait before completing the returned task, or InfiniteTimeSpan to wait indefinitely.

timeProvider: TimeProvider

The TimeProvider with which to interpret delay.

cancellationToken: CancellationToken

A cancellation token to observe while waiting for the task to complete.

Returns

Task

A task that represents the time delay.

Exceptions

ArgumentOutOfRangeException

delay represents a negative time interval other than InfiniteTimeSpan.

-or-

delay's TotalMilliseconds property is greater than 4294967294.

ArgumentNullException

The timeProvider argument is null.

OperationCanceledException

The cancellation token was canceled. This exception is stored into the returned task.

Applies to

Share via

Task.Delay Method

Definition

Overloads

Delay(Int32)

Parameters

Returns

Exceptions

Examples

Remarks

Applies to

Delay(TimeSpan)

Parameters

Returns

Exceptions

Examples

Remarks

Applies to

Delay(Int32, CancellationToken)

Parameters

Returns

Exceptions

Examples

Remarks

Applies to

Delay(TimeSpan, CancellationToken)

Parameters

Returns

Exceptions

Examples

Remarks

Applies to

Delay(TimeSpan, TimeProvider)

Parameters

Returns

Exceptions

Applies to

Delay(TimeSpan, TimeProvider, CancellationToken)

Parameters

Returns

Exceptions

Applies to

Additional resources