Ninject-当RequestScope无意义时，DbContext应该绑定在哪个范围内? [英] Ninject - In what scope DbContext should get binded when RequestScope is meaningless?

问题描述

在MVC/WebAPI环境中，我将使用InRequestScope绑定DbContext.

In an MVC / WebAPI environment I would use InRequestScope to bind the DbContext.

但是，我现在是在控制台应用程序/Windows服务/Azure工作角色上(这并不重要，只是没有Web请求作用域)，它会定期创建许多异步运行的Tasks.我希望每个任务都有自己的DbContext，并且由于任务在各自的线程上运行，因此我尝试使用InThreadScope绑定DbContext.

However, I am now on a Console application / Windows service / Azure worker role (doesn't really matter, just there's no Web request scope), which periodically creates a number of Tasks that run asynchronously. I would like each task to have its own DbContext, and since tasks run on their own thread, I tried binding DbContext using InThreadScope.

不幸的是，我意识到在完成任务时不会释放DbContext.实际发生的情况是，线程返回到线程池，并且在为其分配了新任务时，它已经具有一个DbContext，因此DbContext可以永远保持活动状态.

Unfortunately, I realize that the DbContext is not disposed when a task is finished. What actually happens is, the thread returns to the Thread Pool and when it is assigned a new task, it already has a DbContext, so DbContexts stay alive forever.

这里是否可以使用InThreadScope的方式，还是应该使用其他范围?当线程不时从ThreadPool返回时，如何使用ThreadScope?

Is there a way InThreadScope can be used here or should I use some other scope? How can ThreadScope be used when threads are returning from ThreadPool every now and then?

推荐答案

如果您决定继续使用自定义范围，则解决方案是:

If you decide to go on with custom scope, the solution is:

public sealed class CurrentScope : INotifyWhenDisposed
{
    [ThreadStatic]
    private static CurrentScope currentScope;

    private CurrentScope()
    {
    }

    public static CurrentScope Instance => currentScope ?? (currentScope = new CurrentScope());

    public bool IsDisposed { get; private set; }

    public event EventHandler Disposed;

    public void Dispose()
    {
        this.IsDisposed = true;
        currentScope = null;
        if (this.Disposed != null)
        {
            this.Disposed(this, EventArgs.Empty);
        }
    }
}

绑定:

Bind<DbContext>().To<MyDbContext>().InScope(c => CurrentScope.Instance)

最后:

using (CurrentScope.Instance)
{
    // your request...
    // you'll get always the same DbContext inside of this using block
    // DbContext will be disposed after going out of scope of this using block
}

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