CLR via C# 讀書筆記 3-1 一種單一實例應用程式的實現(訊號量)

單一實例應用程式指的是在你的作業系統中你只能開一個的程式

例如說outlook

以下代碼通過 Semaphore 實行了一個單一實例的控制

(事實上你使用EventWaitHandle 或者 Mutex都是可以的)

原理是因為windows不允許重名的核心對象 ,例子中是 "SomeUniqueStringIdentifyingMyApp"

第一次調用Semaphore的時候,系統將建立一個對象並將createdNew設定為true

第二次調用Semaphore的時候,系統返回現有同名對象並將createdNew設定為false

 

using System;
using System.Threading;
public static class Program
{
public static void Main()
    {
        Boolean createdNew;
// Try to create a kernel object with the specified name
        using (new Semaphore(0, 1, "SomeUniqueStringIdentifyingMyApp", out createdNew))
        {
if (createdNew)
            {
// This thread created the kernel object so no other instance of this
// application must be running. Run the rest of the application here...
            }
else
            {
// This thread opened an existing kernel object with the same string name;
// another instance of this application must be running now.
// There is nothing to do in here, let's just return from Main to terminate
// this second instance of the application.
            }
        }
    }
}