Calling Synchronous Methods Asynchronously
.NET enables you to call any method asynchronously. To do this, you define a delegate with the same signature as the method you want to call. The common language runtime automatically defines BeginInvoke and EndInvoke methods for this delegate, with the appropriate signatures.
Note
Asynchronous delegate calls, specifically the BeginInvoke and EndInvoke methods, are not supported in the .NET Compact Framework.
The BeginInvoke method initiates the asynchronous call. It has the same parameters as the method that you want to execute asynchronously, plus two additional optional parameters. The first parameter is an AsyncCallback delegate that references a method to be called when the asynchronous call completes. The second parameter is a user-defined object that passes information into the callback method. BeginInvoke returns immediately and does not wait for the asynchronous call to complete. BeginInvoke returns an IAsyncResult, which can be used to monitor the progress of the asynchronous call.
The EndInvoke method retrieves the results of the asynchronous call. It can be called any time after BeginInvoke. If the asynchronous call has not completed, EndInvoke blocks the calling thread until it completes. The parameters of EndInvoke include the out and ref parameters (<Out> ByRef and ByRef in Visual Basic) of the method that you want to execute asynchronously, plus the IAsyncResult returned by BeginInvoke.
Note
The IntelliSense feature in Visual Studio displays the parameters of BeginInvoke and EndInvoke. If you're not using Visual Studio or a similar tool, or if you're using C# with Visual Studio, see Asynchronous Programming Model (APM) for a description of the parameters defined for these methods.
The code examples in this topic demonstrate four common ways to use BeginInvoke and EndInvoke to make asynchronous calls. After calling BeginInvoke you can do the following:
Do some work and then call
EndInvoketo block until the call completes.Obtain a WaitHandle using the IAsyncResult.AsyncWaitHandle property, use its WaitOne method to block execution until the WaitHandle is signaled, and then call
EndInvoke.Poll the IAsyncResult returned by
BeginInvoketo determine when the asynchronous call has completed, and then callEndInvoke.Pass a delegate for a callback method to
BeginInvoke. The method is executed on a ThreadPool thread when the asynchronous call completes. The callback method callsEndInvoke.
Important
No matter which technique you use, always call EndInvoke to complete your asynchronous call.
Defining the Test Method and Asynchronous Delegate
The code examples that follow demonstrate various ways of calling the same long-running method, TestMethod, asynchronously. The TestMethod method displays a console message to show that it has begun processing, sleeps for a few seconds, and then ends. TestMethod has an out parameter to demonstrate the way such parameters are added to the signatures of BeginInvoke and EndInvoke. You can handle ref parameters similarly.
The following code example shows the definition of TestMethod and the delegate named AsyncMethodCaller that can be used to call TestMethod asynchronously. To compile the code examples, you must include the definitions for TestMethod and the AsyncMethodCaller delegate.
using namespace System;
using namespace System::Threading;
using namespace System::Runtime::InteropServices;
namespace Examples {
namespace AdvancedProgramming {
namespace AsynchronousOperations
{
public ref class AsyncDemo
{
public:
// The method to be executed asynchronously.
String^ TestMethod(int callDuration, [OutAttribute] int% threadId)
{
Console::WriteLine("Test method begins.");
Thread::Sleep(callDuration);
threadId = Thread::CurrentThread->ManagedThreadId;
return String::Format("My call time was {0}.", callDuration);
}
};
// The delegate must have the same signature as the method
// it will call asynchronously.
public delegate String^ AsyncMethodCaller(int callDuration, [OutAttribute] int% threadId);
}}}
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);
}
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncDemo
' The method to be executed asynchronously.
Public Function TestMethod(ByVal callDuration As Integer, _
<Out> ByRef threadId As Integer) As String
Console.WriteLine("Test method begins.")
Thread.Sleep(callDuration)
threadId = Thread.CurrentThread.ManagedThreadId()
return String.Format("My call time was {0}.", callDuration.ToString())
End Function
End Class
' The delegate must have the same signature as the method
' it will call asynchronously.
Public Delegate Function AsyncMethodCaller(ByVal callDuration As Integer, _
<Out> ByRef threadId As Integer) As String
End Namespace
Waiting for an Asynchronous Call with EndInvoke
The simplest way to execute a method asynchronously is to start executing the method by calling the delegate's BeginInvoke method, do some work on the main thread, and then call the delegate's EndInvoke method. EndInvoke might block the calling thread because it does not return until the asynchronous call completes. This is a good technique to use with file or network operations.
Important
Because EndInvoke might block, you should never call it from threads that service the user interface.
#using <TestMethod.dll>
using namespace System;
using namespace System::Threading;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;
void main()
{
// The asynchronous method puts the thread id here.
int threadId = 2546;
// Create an instance of the test class.
AsyncDemo^ ad = gcnew AsyncDemo();
// Create the delegate.
AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);
// Initiate the asynchronous call.
IAsyncResult^ result = caller->BeginInvoke(3000,
threadId, nullptr, nullptr);
Thread::Sleep(1);
Console::WriteLine("Main thread {0} does some work.",
Thread::CurrentThread->ManagedThreadId);
// Call EndInvoke to wait for the asynchronous call to complete,
// and to retrieve the results.
String^ returnValue = caller->EndInvoke(threadId, result);
Console::WriteLine("The call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
/* This example produces output similar to the following:
Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
*/
using System;
using System.Threading;
namespace Examples.AdvancedProgramming.AsynchronousOperations
{
public class AsyncMain
{
public 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 asynchronous call.
IAsyncResult result = caller.BeginInvoke(3000,
out threadId, null, null);
Thread.Sleep(0);
Console.WriteLine("Main thread {0} does some work.",
Thread.CurrentThread.ManagedThreadId);
// Call EndInvoke to wait for the asynchronous call to complete,
// and to retrieve the results.
string returnValue = caller.EndInvoke(out threadId, result);
Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
}
}
/* This example produces output similar to the following:
Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
*/
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncMain
Shared Sub Main()
' The asynchronous method puts the thread id here.
Dim threadId As Integer
' Create an instance of the test class.
Dim ad As New AsyncDemo()
' Create the delegate.
Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
' Initiate the asynchronous call.
Dim result As IAsyncResult = caller.BeginInvoke(3000, _
threadId, Nothing, Nothing)
Thread.Sleep(0)
Console.WriteLine("Main thread {0} does some work.", _
Thread.CurrentThread.ManagedThreadId)
' Call EndInvoke to Wait for the asynchronous call to complete,
' and to retrieve the results.
Dim returnValue As String = caller.EndInvoke(threadId, result)
Console.WriteLine("The call executed on thread {0}, with return value ""{1}"".", _
threadId, returnValue)
End Sub
End Class
End Namespace
'This example produces output similar to the following:
'
'Main thread 1 does some work.
'Test method begins.
'The call executed on thread 3, with return value "My call time was 3000.".
Waiting for an Asynchronous Call with WaitHandle
You can obtain a WaitHandle by using the AsyncWaitHandle property of the IAsyncResult returned by BeginInvoke. The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.
If you use a WaitHandle, you can perform additional processing before or after the asynchronous call completes, but before calling EndInvoke to retrieve the results.
Note
The wait handle is not closed automatically when you call EndInvoke. If you release all references to the wait handle, system resources are freed when garbage collection reclaims the wait handle. To free the system resources as soon as you are finished using the wait handle, dispose of it by calling the WaitHandle.Close method. Garbage collection works more efficiently when disposable objects are explicitly disposed.
#using <TestMethod.dll>
using namespace System;
using namespace System::Threading;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;
void main()
{
// The asynchronous method puts the thread id here.
int threadId;
// Create an instance of the test class.
AsyncDemo^ ad = gcnew AsyncDemo();
// Create the delegate.
AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);
// Initiate the asynchronous call.
IAsyncResult^ result = caller->BeginInvoke(3000,
threadId, nullptr, nullptr);
Thread::Sleep(0);
Console::WriteLine("Main thread {0} does some work.",
Thread::CurrentThread->ManagedThreadId);
// Wait for the WaitHandle to become signaled.
result->AsyncWaitHandle->WaitOne();
// Perform additional processing here.
// Call EndInvoke to retrieve the results.
String^ returnValue = caller->EndInvoke(threadId, result);
// Close the wait handle.
result->AsyncWaitHandle->Close();
Console::WriteLine("The call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
/* This example produces output similar to the following:
Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
*/
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 asynchronous call.
IAsyncResult result = caller.BeginInvoke(3000,
out threadId, null, null);
Thread.Sleep(0);
Console.WriteLine("Main thread {0} does some work.",
Thread.CurrentThread.ManagedThreadId);
// Wait for the WaitHandle to become signaled.
result.AsyncWaitHandle.WaitOne();
// Perform additional processing here.
// Call EndInvoke to retrieve the results.
string returnValue = caller.EndInvoke(out threadId, result);
// Close the wait handle.
result.AsyncWaitHandle.Close();
Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
}
}
/* This example produces output similar to the following:
Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
*/
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncMain
Shared Sub Main()
' The asynchronous method puts the thread id here.
Dim threadId As Integer
' Create an instance of the test class.
Dim ad As New AsyncDemo()
' Create the delegate.
Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
' Initiate the asynchronous call.
Dim result As IAsyncResult = caller.BeginInvoke(3000, _
threadId, Nothing, Nothing)
Thread.Sleep(0)
Console.WriteLine("Main thread {0} does some work.", _
Thread.CurrentThread.ManagedThreadId)
' Perform additional processing here and then
' wait for the WaitHandle to be signaled.
result.AsyncWaitHandle.WaitOne()
' Call EndInvoke to retrieve the results.
Dim returnValue As String = caller.EndInvoke(threadId, result)
' Close the wait handle.
result.AsyncWaitHandle.Close()
Console.WriteLine("The call executed on thread {0}, with return value ""{1}"".", _
threadId, returnValue)
End Sub
End Class
End Namespace
'This example produces output similar to the following:
'
'Main thread 1 does some work.
'Test method begins.
'The call executed on thread 3, with return value "My call time was 3000.".
Polling for Asynchronous Call Completion
You can use the IsCompleted property of the IAsyncResult returned by BeginInvoke to discover when the asynchronous call completes. You might do this 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.
#using <TestMethod.dll>
using namespace System;
using namespace System::Threading;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;
void main()
{
// The asynchronous method puts the thread id here.
int threadId;
// Create an instance of the test class.
AsyncDemo^ ad = gcnew AsyncDemo();
// Create the delegate.
AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);
// Initiate the asynchronous call.
IAsyncResult^ result = caller->BeginInvoke(3000,
threadId, nullptr, nullptr);
// Poll while simulating work.
while(result->IsCompleted == false)
{
Thread::Sleep(250);
Console::Write(".");
}
// Call EndInvoke to retrieve the results.
String^ returnValue = caller->EndInvoke(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.".
*/
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 asynchronous call.
IAsyncResult result = caller.BeginInvoke(3000,
out threadId, null, null);
// Poll while simulating work.
while(result.IsCompleted == false) {
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.".
*/
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncMain
Shared Sub Main()
' The asynchronous method puts the thread id here.
Dim threadId As Integer
' Create an instance of the test class.
Dim ad As New AsyncDemo()
' Create the delegate.
Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
' Initiate the asynchronous call.
Dim result As IAsyncResult = caller.BeginInvoke(3000, _
threadId, Nothing, Nothing)
' Poll while simulating work.
While result.IsCompleted = False
Thread.Sleep(250)
Console.Write(".")
End While
' Call EndInvoke to retrieve the results.
Dim returnValue As String = caller.EndInvoke(threadId, result)
Console.WriteLine(vbCrLf & _
"The call executed on thread {0}, with return value ""{1}"".", _
threadId, returnValue)
End Sub
End Class
End Namespace
' 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.".
Executing a Callback Method When an Asynchronous Call Completes
If the thread that initiates the asynchronous call does not need to be the thread that processes the results, you can execute a callback method when the call completes. The callback method is executed on a ThreadPool thread.
To use a callback method, you must pass BeginInvoke an AsyncCallback delegate that represents the callback method. You can also pass an object that contains information to be used by the callback method. In the callback method, you can cast the IAsyncResult, which is the only parameter of the callback method, to an AsyncResult object. You can then use the AsyncResult.AsyncDelegate property to get the delegate that was used to initiate the call so that you can call EndInvoke.
Notes on the example:
The
threadIdparameter ofTestMethodis anoutparameter ([<Out>ByRefin Visual Basic), so its input value is never used byTestMethod. A dummy variable is passed to theBeginInvokecall. If thethreadIdparameter were arefparameter (ByRefin Visual Basic), the variable would have to be a class-level field so that it could be passed to bothBeginInvokeandEndInvoke.The state information that is passed to
BeginInvokeis a format string, which the callback method uses to format an output message. Because it is passed as type Object, the state information must be cast to its proper type before it can be used.The callback is made on a ThreadPool thread. ThreadPool threads are background threads, which do not keep the application running if the main thread ends, so the main thread of the example has to sleep long enough for the callback to finish.
#using <TestMethod.dll>
using namespace System;
using namespace System::Threading;
using namespace System::Runtime::Remoting::Messaging;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;
// The callback method must have the same signature as the
// AsyncCallback delegate.
void CallbackMethod(IAsyncResult^ ar)
{
// Retrieve the delegate.
AsyncResult^ result = (AsyncResult^) ar;
AsyncMethodCaller^ caller = (AsyncMethodCaller^) result->AsyncDelegate;
// Retrieve the format string that was passed as state
// information.
String^ formatString = (String^) ar->AsyncState;
// Define a variable to receive the value of the out parameter.
// If the parameter were ref rather than out then it would have to
// be a class-level field so it could also be passed to BeginInvoke.
int threadId = 0;
// Call EndInvoke to retrieve the results.
String^ returnValue = caller->EndInvoke(threadId, ar);
// Use the format string to format the output message.
Console::WriteLine(formatString, threadId, returnValue);
};
void main()
{
// Create an instance of the test class.
AsyncDemo^ ad = gcnew AsyncDemo();
// Create the delegate.
AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);
// The threadId parameter of TestMethod is an out parameter, so
// its input value is never used by TestMethod. Therefore, a dummy
// variable can be passed to the BeginInvoke call. If the threadId
// parameter were a ref parameter, it would have to be a class-
// level field so that it could be passed to both BeginInvoke and
// EndInvoke.
int dummy = 0;
// Initiate the asynchronous call, passing three seconds (3000 ms)
// for the callDuration parameter of TestMethod; a dummy variable
// for the out parameter (threadId); the callback delegate; and
// state information that can be retrieved by the callback method.
// In this case, the state information is a string that can be used
// to format a console message.
IAsyncResult^ result = caller->BeginInvoke(3000,
dummy,
gcnew AsyncCallback(&CallbackMethod),
"The call executed on thread {0}, with return value \"{1}\".");
Console::WriteLine("The main thread {0} continues to execute...",
Thread::CurrentThread->ManagedThreadId);
// The callback is made on a ThreadPool thread. ThreadPool threads
// are background threads, which do not keep the application running
// if the main thread ends. Comment out the next line to demonstrate
// this.
Thread::Sleep(4000);
Console::WriteLine("The main thread ends.");
}
/* This example produces output similar to the following:
The main thread 1 continues to execute...
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
The main thread ends.
*/
using System;
using System.Threading;
using System.Runtime.Remoting.Messaging;
namespace Examples.AdvancedProgramming.AsynchronousOperations
{
public class AsyncMain
{
static void Main()
{
// Create an instance of the test class.
AsyncDemo ad = new AsyncDemo();
// Create the delegate.
AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);
// The threadId parameter of TestMethod is an out parameter, so
// its input value is never used by TestMethod. Therefore, a dummy
// variable can be passed to the BeginInvoke call. If the threadId
// parameter were a ref parameter, it would have to be a class-
// level field so that it could be passed to both BeginInvoke and
// EndInvoke.
int dummy = 0;
// Initiate the asynchronous call, passing three seconds (3000 ms)
// for the callDuration parameter of TestMethod; a dummy variable
// for the out parameter (threadId); the callback delegate; and
// state information that can be retrieved by the callback method.
// In this case, the state information is a string that can be used
// to format a console message.
IAsyncResult result = caller.BeginInvoke(3000,
out dummy,
new AsyncCallback(CallbackMethod),
"The call executed on thread {0}, with return value \"{1}\".");
Console.WriteLine("The main thread {0} continues to execute...",
Thread.CurrentThread.ManagedThreadId);
// The callback is made on a ThreadPool thread. ThreadPool threads
// are background threads, which do not keep the application running
// if the main thread ends. Comment out the next line to demonstrate
// this.
Thread.Sleep(4000);
Console.WriteLine("The main thread ends.");
}
// The callback method must have the same signature as the
// AsyncCallback delegate.
static void CallbackMethod(IAsyncResult ar)
{
// Retrieve the delegate.
AsyncResult result = (AsyncResult) ar;
AsyncMethodCaller caller = (AsyncMethodCaller) result.AsyncDelegate;
// Retrieve the format string that was passed as state
// information.
string formatString = (string) ar.AsyncState;
// Define a variable to receive the value of the out parameter.
// If the parameter were ref rather than out then it would have to
// be a class-level field so it could also be passed to BeginInvoke.
int threadId = 0;
// Call EndInvoke to retrieve the results.
string returnValue = caller.EndInvoke(out threadId, ar);
// Use the format string to format the output message.
Console.WriteLine(formatString, threadId, returnValue);
}
}
}
/* This example produces output similar to the following:
The main thread 1 continues to execute...
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
The main thread ends.
*/
Imports System.Threading
Imports System.Runtime.Remoting.Messaging
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncMain
Shared Sub Main()
' Create an instance of the test class.
Dim ad As New AsyncDemo()
' Create the delegate.
Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
' The threadId parameter of TestMethod is an <Out> parameter, so
' its input value is never used by TestMethod. Therefore, a dummy
' variable can be passed to the BeginInvoke call. If the threadId
' parameter were a ByRef parameter, it would have to be a class-
' level field so that it could be passed to both BeginInvoke and
' EndInvoke.
Dim dummy As Integer = 0
' Initiate the asynchronous call, passing three seconds (3000 ms)
' for the callDuration parameter of TestMethod; a dummy variable
' for the <Out> parameter (threadId); the callback delegate; and
' state information that can be retrieved by the callback method.
' In this case, the state information is a string that can be used
' to format a console message.
Dim result As IAsyncResult = caller.BeginInvoke(3000, _
dummy, _
AddressOf CallbackMethod, _
"The call executed on thread {0}, with return value ""{1}"".")
Console.WriteLine("The main thread {0} continues to execute...", _
Thread.CurrentThread.ManagedThreadId)
' The callback is made on a ThreadPool thread. ThreadPool threads
' are background threads, which do not keep the application running
' if the main thread ends. Comment out the next line to demonstrate
' this.
Thread.Sleep(4000)
Console.WriteLine("The main thread ends.")
End Sub
' The callback method must have the same signature as the
' AsyncCallback delegate.
Shared Sub CallbackMethod(ByVal ar As IAsyncResult)
' Retrieve the delegate.
Dim result As AsyncResult = CType(ar, AsyncResult)
Dim caller As AsyncMethodCaller = CType(result.AsyncDelegate, AsyncMethodCaller)
' Retrieve the format string that was passed as state
' information.
Dim formatString As String = CType(ar.AsyncState, String)
' Define a variable to receive the value of the <Out> parameter.
' If the parameter were ByRef rather than <Out> then it would have to
' be a class-level field so it could also be passed to BeginInvoke.
Dim threadId As Integer = 0
' Call EndInvoke to retrieve the results.
Dim returnValue As String = caller.EndInvoke(threadId, ar)
' Use the format string to format the output message.
Console.WriteLine(formatString, threadId, returnValue)
End Sub
End Class
End Namespace
' This example produces output similar to the following:
'
'The main thread 1 continues to execute...
'Test method begins.
'The call executed on thread 3, with return value "My call time was 3000.".
'The main thread ends.
