IAsyncResult.IsCompleted Property

Definition

Namespace:

System

Assemblies:

netstandard.dll, System.Runtime.dll

Gets a value that indicates whether the asynchronous operation has completed.

C#

public bool IsCompleted { get; }

Property Value

Boolean

true if the operation is complete; otherwise, false.

Examples

The following example shows how to use the IsCompleted property of the IAsyncResult to discover when an asynchronous call completes. In this case, the asynchronous call is made by using the BeginInvoke method of a delegate. You might use the IsCompleted property to poll for completion when making the asynchronous call from a thread that services the user interface. Polling for completion allows the calling thread to continue executing while the asynchronous call executes on a ThreadPool thread.

The example consists of two classes: the class that contains the method that is called asynchronously, and the class that contains the Main method that makes the call.

For more information and more examples of calling methods asynchronously by using delegates, see Calling Synchronous Methods Asynchronously.

C#

using System;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncDemo
    {
        // The method to be executed asynchronously.
        public string TestMethod(int callDuration, out int threadId)
        {
            Console.WriteLine("Test method begins.");
            Thread.Sleep(callDuration);
            threadId = Thread.CurrentThread.ManagedThreadId;
            return String.Format("My call time was {0}.", callDuration.ToString());
        }
    }
    // The delegate must have the same signature as the method
    // it will call asynchronously.
    public delegate string AsyncMethodCaller(int callDuration, out int threadId);
}

C#

using System;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncMain
    {
        static void Main() {
            // The asynchronous method puts the thread id here.
            int threadId;

            // Create an instance of the test class.
            AsyncDemo ad = new AsyncDemo();

            // Create the delegate.
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

            // Initiate the asychronous call.
            IAsyncResult result = caller.BeginInvoke(3000,
                out threadId, null, null);

            // Poll while simulating work.
            while(!result.IsCompleted) {
                Thread.Sleep(250);
                Console.Write(".");
            }

            // Call EndInvoke to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, result);

            Console.WriteLine("\nThe call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

/* This example produces output similar to the following:

Test method begins.
.............
The call executed on thread 3, with return value "My call time was 3000.".
 */

Remarks

When this property is true, you can assume it is safe to discard any resources you allocate for use by the asynchronous operation.

Notes to Implementers

Implementers will typically return the value of a private field or internal test as the value of this property.

Notes to Callers

Clients that poll for operation status (as opposed to waiting on a synchronization object) use this property to determine the status of the operation.

Applies to