c# - 设置一次静态字段值并在所有其他线程中使用最新设置的值

Question

在处理多线程应用程序时，我曾经遇到过需要为静态字段赋值的情况。我想在所有其余线程中使用静态字段的最新值。

代码如下:

Main() 方法:

for (var i = 1; i <= 50; i++)
{
  ProcessEmployee processEmployee = new ProcessEmployee();

  Thread thread = new Thread(processEmployee.Process);
  thread.Start(i);
}

public class ProcessEmployee
    {
        public void Process(object s)
        {

            // Sometimes I get value 0 even if the value set to 1 by other thread.
            // Want to resolve this issue.
            if (StaticContainer.LastValue == 0)
            {
                Console.WriteLine("Last value is 0");

            }

            if (Convert.ToInt32(s) == 5)
            {
                StaticContainer.LastValue = 1;
                Console.WriteLine("Last Value is set to 1");
            }

            // Expectation: want to get last value = 1 in all rest of the threads. 
            Console.WriteLine(StaticContainer.LastValue);
        }
    }

public static class StaticContainer
    {
        private static int lastValue = 0;

        public static int LastValue
        {
            get
            {
                return lastValue;
            }
            set
            {
                lastValue = value;
            }
        }
    }

问题:

基本上，我想知道，一旦我通过任何线程为静态字段设置特定值，我想获得相同的值(另一个thread设置的最新值) )始终在 threads 的其余部分中。

请告诉我对此的任何想法。

提前致谢!

Answer 1

Basically, I want to know that once I set specific value to static field by any thread, I want to get the same value (latest value set by another thread) in rest of the threads always.

听起来你基本上错过了一个内存障碍。您可以使用显式屏障但不使用锁来解决这个问题 - 或者您可以采用强力锁定方法，或者您可以使用Interlocked:

private static int lastValue;

public int LastValue
{
    // This won't actually change the value - basically if the value *was* 0,
    // it gets set to 0 (no change). If the value *wasn't* 0, it doesn't get
    // changed either.
    get { return Interlocked.CompareExchange(ref lastValue, 0, 0); }

    // This will definitely change the value - we ignore the return value, because
    // we don't need it.
    set { Interlocked.Exchange(ref lastValue, value); }
}

您可以按照newStackExchangeInstance在评论中的建议使用 volatile - 但我实际上不确定我完全理解确切它的含义，我强烈怀疑它的含义并不像大多数人所认为的那样，或者确实与 MSDN 文档所述的那样。您可能想阅读Joe Duffy's blog post on it ( and this one too ) 了解更多背景信息。