How to call a function asynchronizly in C# # Page1- Delegate.begininvoke, endinvoke


BeginInvoke and EndInvoke

we use four ways to process the asynchronozed call.i.e. EndInvoke,WaitHandler,IsComplete,callbackfunction.they are properties of IAsyncresult.

  1. we can see description from MSDN,

    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 ( ByRef and ByRef in Visual Basic) of the method that you want to execute asynchronously, plus the IAsyncResult returned by BeginInvoke.

code example:

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);
}
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 asychronous 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.".
*/

code example : Waiting for an Asynchronous Call with WaitHandle

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); 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.".
*/

code example 3: 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 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 == 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.".
*/

code example4: 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.

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.
*/
  1. Some reference link about concept: AsyncCallback, IAsyncResult

  2. 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.

we can refer AsyncWaitHandle, WaitHandle

How to Call a synchronize function asynchronizly in C#的更多相关文章

  1. HOW TO: Synchronize changes when completing a P2V or V2V with VMware vCenter Converter Standalone 5.1

    http://www.experts-exchange.com/Software/VMWare/A_11489-HOW-TO-Synchronize-changes-when-completing-a ...

  2. Neural Style学习2——环境安装

    neural-style Installation This guide will walk you through the setup for neural-style on Ubuntu. Ste ...

  3. murri

    github: https://github.com/haltu/muuri 官网:https://haltu.github.io/muuri/   安装 npm install murri —sav ...

  4. 通过百度echarts实现数据图表展示功能

    现在我们在工作中,在开发中都会或多或少的用到图表统计数据显示给用户.通过图表可以很直观的,直接的将数据呈现出来.这里我就介绍说一下利用百度开源的echarts图表技术实现的具体功能. 1.对于不太理解 ...

  5. Delphi中线程类TThread实现多线程编程2---事件、临界区、Synchronize、WaitFor……

    接着上文介绍TThread. 现在开始说明 Synchronize和WaitFor 但是在介绍这两个函数之前,需要先介绍另外两个线程同步技术:事件和临界区 事件(Event) 事件(Event)与De ...

  6. Synchronization in Delphi TThread class : Synchronize, Queue

    http://embarcadero.newsgroups.archived.at/public.delphi.rtl/201112/1112035763.html > Hi,>> ...

  7. AsyncCalls – Asynchronous function calls

    AsyncCalls – Asynchronous function callsWith AsyncCalls you can execute multiple functions at the sa ...

  8. Synchronize执行过程

    Synchronize执行过程及原理 在windows原生应用程序开发中,经常伴随多线程的使用,多线程开发很简单,难点就是在于线程的同步,在Delphi中提供了VC中不具备的一个过程Synchroni ...

  9. [React] Use the React Effect Hook in Function Components

    Similar to the State Hook, the Effect Hook is “first-class” in React and handy for performing side e ...

随机推荐

  1. 关键字 base 的作用

    ①调用基类上已被其他方法重写的方法,小栗子a如下: public class Father { public virtual void Show() { Console.WriteLine(" ...

  2. 可视化日志分析工具Gltail的安装与使用

    可视化日志分析工具Gltail的安装与使用      GlTail.rb 是一款带有浓郁的 Geek 风格的可视化日志分析工具,它采用 Ruby 技术构建,并利用 OpenGL 图形技术进行渲染,呈现 ...

  3. def

    a = 97,A = 65,z = 122,Z = 90 小写字母比大写字母整形数值高,upper->lower相差32 把小写字母转化成大写字母,将小写字母 - 32 1. typedef 数 ...

  4. NHibernate输出SQL语句

    用了NHierbate之后,很少需要写原生的SQL语句,由于总是看不到SQL语句,所以有时候对SQL调优非常不利.因此产生了让NHibernate输出它所生成的SQL语句的想法,以便于后续调优. 一. ...

  5. global.autoindex dede:global.itemindex 获取子栏目自动排序序号

    {dede:channel  row='6' typeid=7 }                  [field:global.autoindex runphp='yes']             ...

  6. IP配置

    1: #vi /etc/sysconfig/network-scripts/ifcfg-eth0 2: 实验环境-网络设置 公司域网: IP=162.168.16.0/24 netmask=255.2 ...

  7. iOS NSString中字符串的删除,替换

  8. eclipse自动补全

    最简单的修改方式是:Windows——>Preferences——>Java-->Editor-->Content Asist,在Auto activation trigger ...

  9. cpack

    一. 简介 CPack是CMake 2.4.2之后的一个内置工具,主要作用就是生成制定类型的安装包.它可以脱离cmake单独运行. 二. 基本设置 (mandatory) 设置包类型set(CPACK ...

  10. jQuery中$(function() {});问题详解

    $(function() {});是$(document).ready(function(){ })的简写,最早接触的时候也说$(document).ready(function(){ })这个函数是 ...