Question

我有一个可以通过SDK（项目中引用的.DLL文件）控制的硬件组件。我试图实现一个辅助类来处理对象的实例化，并为每个需要它的窗口提供所需的object reference。这就是我在窗口后面的代码中创建对象的方法：

    //private fields
    SystemConnector myConn; 
    MyHardware mySystem; // this is the object i need a reference to

    public Window1()
    {
        InitializeComponent();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        SystemDiscoverer SystemDiscoverer = new SystemDiscoverer();
        SystemDiscoverer.Discovered += (sysInfo) =>
        {
            myConn = new SystemConnector(sysInfo.IPAddress);

            if (myConn != null)
                mySystem = new MyHardware(myConn);

        };
        SystemDiscoverer.Discover();
    }

    private void WindowBase_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        if (myConn != null)
            myConn.Dispose();

        if (mySystem != null)
            mySystem.Dispose();
    }

我想把这个逻辑转移到帮助类中，但我有一些问题我无法找到解决方案：

我能找到的所有Singleton示例都是针对自定义对象的并没有解释引用对象的使用。
如何处理对象的创建，因为它是在事件处理程序内完成的？

Answer 1

要从事件处理程序处理创建，请尝试：

        LazyInitializer.EnsureInitialized(...)

它是线程安全的，所以你应该能够为你的单身人士初始化一个静态属性。

MSDN文章：

http://blogs.msdn.com/b/jolud/archive/2010/04/02/initialization-of-shared-resources.aspx

一个例子，来自ASP.NET MVC 4标准项目模板。

    public sealed class InitializeSimpleMembershipAttribute : ActionFilterAttribute {
    private static SimpleMembershipInitializer _initializer;
    private static object _initializerLock = new object();
    private static bool _isInitialized;

    public override void OnActionExecuting(ActionExecutingContext filterContext) {
        // Ensure ASP.NET Simple Membership is initialized only once per app start
        LazyInitializer.EnsureInitialized(ref _initializer, ref _isInitialized, ref _initializerLock);
    }

    private class SimpleMembershipInitializer {
        public SimpleMembershipInitializer() {
            Database.SetInitializer<UsersContext>(null);

            try {
                using(var context = new UsersContext()) {
                    if(!context.Database.Exists()) {
                        // Create the SimpleMembership database without Entity Framework migration schema
                        ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
                    }
                }

                WebSecurity.InitializeDatabaseConnection("DefaultConnection", "UserProfile", "UserId", "UserName", autoCreateTables: true);
            }
            catch(Exception ex) {
                throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized. For more information, please see http://go.microsoft.com/fwlink/?LinkId=256588", ex);
            }
        }
    }
}

Answer 2

我会用MyHardware方法将async类包装在一个包含SystemDiscoverer.Discovered事件的public sealed class MyHardwareSingleton { static MyHardwareSingleton() { } private MyHardwareSingleton() { } private static readonly MyHardwareSingleton _myHardware = new MyHardwareSingleton(); private SystemConnector _myConn; private MyHardware _mySystem; public MyHardwareSingleton Instance { get { return _myHardware; } } public Task<MyHardware> GetHardwareAsync() { if (_mySystem != null) { return Task.FromResult(_mySystem); } var tcs = new TaskCompletionSource<MyHardware>(); SystemDiscoverer SystemDiscoverer = new SystemDiscoverer(); SystemDiscoverer.Discovered += (sysInfo) => { myConn = new SystemConnector(sysInfo.IPAddress); if (myConn != null) { mySystem = new MyHardware(myConn); tcs.TrySetResult(mySystem); return tcs.Task; } // This indicated that myConn came back null. tcs.TrySetResult(null); return tcs.Task; }; // Make SystemDiscoverer run asynchrnously. We will await it so when it completes we will get the desired MyHardware instance. SystemDiscoverer.DiscoverAsync(); return tcs.Task; } }方法中：

SystemConnector

可以在public Task DiscoverAsync() { return Task.Run(() => Discover()); }类中添加DiscoverAsync，如下所示：

private async void Window_Loaded(object sender, RoutedEventArgs e)
{
     var myHardware = await MyHardwareSingleton.Instance.DiscoverAsync();
}

然后您可以通过以下代码从代码中调用它：

{{1}}

当然，我没有处理任何异常处理/取消。这只是使用TAP

可以完成的示例

为引用的程序集创建单例

2 个答案: