抱歉，伙计们，我不同意锁定这个可能会导致僵局的说法。你混淆了两件事:僵局和饥饿。

如果不中断其中一个线程，就无法取消死锁，因此进入死锁后就无法退出 饥饿将在其中一个线程完成其工作后自动结束

这里有一张图可以说明两者的区别。

结论 如果线程饥饿对您来说不是问题，您仍然可以安全地使用lock(this)。你仍然需要记住，当线程使用lock(this)饿死线程时，它将以锁定对象的锁结束，它最终将以永远饥饿结束;)

如果可以公开访问实例，就会出现问题，因为可能有其他请求正在使用相同的对象实例。最好使用私有/静态变量。

想象一下，你的办公室有一位技术娴熟的秘书，这是部门的共享资源。偶尔，你会因为有任务而冲向他们，只希望你的另一个同事还没有认领他们。通常你只需要等很短的一段时间。

因为关心就是分享，你的经理决定顾客也可以直接使用秘书。但这有一个副作用:当您为该客户工作时，客户甚至可能会认领它们，并且您还需要他们执行部分任务。死锁发生，因为声明不再是层次结构。如果从一开始就不允许客户索赔，这完全可以避免。

lock(this) is bad as we've seen. An outside object might lock on the object and since you don't control who's using the class, anyone can lock on it... Which is the exact example as described above. Again, the solution is to limit exposure of the object. However, if you have a private, protected or internal class you could already control who is locking on your object, because you're sure that you've written your code yourself. So the message here is: don't expose it as public. Also, ensuring that a lock is used in similar scenario's avoids deadlocks.

与此完全相反的是锁定整个应用领域共享的资源——这是最坏的情况。这就像把你的秘书放在外面，让外面的人去认领一样。结果是彻底的混乱——或者就源代码而言:这是一个坏主意;把它扔掉，重新开始。我们怎么做呢?

正如这里大多数人指出的那样，类型在应用领域是共享的。但是我们可以使用更好的东西:字符串。原因是字符串被池化了。换句话说，如果你有两个字符串在一个应用域中有相同的内容，它们有可能有完全相同的指针。由于指针被用作锁键，基本上你得到的是“为未定义的行为做好准备”的同义词。

类似地，你不应该锁定WCF对象HttpContext。目前,线程。当前，单例(一般)等。避免这一切的最简单方法是什么?private [static] object myLock = new object();

以下是一些更容易遵循的示例代码(IMO):(将在LinqPad中工作，参考以下名称空间:System。Net和System.Threading.Tasks)

需要记住的一点是，lock(x)基本上是语法糖，它所做的就是使用Monitor。输入，然后使用try、catch和finally块调用Monitor.Exit。参见:https://learn.microsoft.com/en-us/dotnet/api/system.threading.monitor.enter(备注部分)

或者使用c#锁语句(Visual Basic中的SyncLock语句)， 它将Enter和Exit方法包装在一个try…finally块中。

void Main()
{
    //demonstrates why locking on THIS is BADD! (you should never lock on something that is publicly accessible)
    ClassTest test = new ClassTest();
    lock(test) //locking on the instance of ClassTest
    {
        Console.WriteLine($"CurrentThread {Thread.CurrentThread.ManagedThreadId}");
        Parallel.Invoke(new Action[]
        {
            () => {
                //this is there to just use up the current main thread. 
                Console.WriteLine($"CurrentThread {Thread.CurrentThread.ManagedThreadId}");
                },
            //none of these will enter the lock section.
            () => test.DoWorkUsingThisLock(1),//this will dead lock as lock(x) uses Monitor.Enter
            () => test.DoWorkUsingMonitor(2), //this will not dead lock as it uses Montory.TryEnter
        });
    }
}

public class ClassTest
{
    public void DoWorkUsingThisLock(int i)
    {
        Console.WriteLine($"Start ClassTest.DoWorkUsingThisLock {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
        lock(this) //this can be bad if someone has locked on this already, as it will cause it to be deadlocked!
        {
            Console.WriteLine($"Running: ClassTest.DoWorkUsingThisLock {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
            Thread.Sleep(1000);
        }
        Console.WriteLine($"End ClassTest.DoWorkUsingThisLock Done {i}  CurrentThread {Thread.CurrentThread.ManagedThreadId}");
    }

    public void DoWorkUsingMonitor(int i)
    {
        Console.WriteLine($"Start ClassTest.DoWorkUsingMonitor {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
        if (Monitor.TryEnter(this))
        {
            Console.WriteLine($"Running: ClassTest.DoWorkUsingMonitor {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
            Thread.Sleep(1000);
            Monitor.Exit(this);
        }
        else
        {
            Console.WriteLine($"Skipped lock section!  {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
        }

        Console.WriteLine($"End ClassTest.DoWorkUsingMonitor Done {i} CurrentThread {Thread.CurrentThread.ManagedThreadId}");
        Console.WriteLine();
    }
}

输出

CurrentThread 15
CurrentThread 15
Start ClassTest.DoWorkUsingMonitor 2 CurrentThread 13
Start ClassTest.DoWorkUsingThisLock 1 CurrentThread 12
Skipped lock section!  2 CurrentThread 13
End ClassTest.DoWorkUsingMonitor Done 2 CurrentThread 13

注意线程#12永远不会因为死锁而结束。

请参考下面的链接，它解释了为什么锁(这)不是一个好主意。

https://learn.microsoft.com/en-us/dotnet/standard/threading/managed-threading-best-practices

所以解决方案是添加一个私有对象，例如，lockObject到类中，并将代码区域放在lock语句中，如下所示:

lock (lockObject)
{
...
}

以下是不建议使用的原因。

短版: 考虑下面的代码片段:

object foo = new Object(); 
object bar = foo; 

lock(foo)
{
  lock(bar){}
}  

这里，foo和bar引用的是导致死锁的同一个对象实例。这是现实中可能发生的事情的简化版本。

长版: 为了根据下面的代码片段更详细地解释它，假设您编写了一个类(在本例中为SomeClass)，并且类的使用者(名为“John”的编码器)希望获得类实例(在本例中为someObject)上的锁。他遇到死锁是因为他在实例someObject上获得了一个锁，在这个锁中他调用了该实例的一个方法(SomeMethod())，该方法在内部获得了同一个实例上的锁。

I could have written the following example with or without Task/Thread and the gist of deadlock still remains the same. To prevent bizarre situation where the main Thread finishes while its children are still running, I used .Wait(). However, in long-running-tasks or situation where a code-snippet executes more frequently, you would definitely see the same behavior. Although John applied a bad practice of using an instance of a class as a lock-object, but we (as the developer of a classlibrary SomeClass) should deter such situation simple by not using this as a lock-object in our class. Instead, we should declare a simple private field and use that as our lock-object. using System; using System.Threading; using System.Threading.Tasks; class SomeClass { public void SomeMethod() { //NOTE: Locks over an object that is already locked by the caller. // Hence, the following code-block never executes. lock (this) { Console.WriteLine("Hi"); } } } public class Program { public static void Main() { SomeClass o = new SomeClass(); lock (o) { Task.Run(() => o.SomeMethod()).Wait(); } Console.WriteLine("Finish"); } }