我有代码示例
var options = new ExecutionDataflowBlockOptions();
var actionBlock = new ActionBlock<int>(async request=>{
var rand = new Ranodm();
//do some stuff with request by using rand
},options);
这段代码的问题是,在每个请求中我都必须创建新的
rand
对象。有一种方法可以为每个线程定义一个 rand
对象并在处理请求时重复使用同一对象?
感谢 Reed Copsey 的好文章 和 Theodor Zoulias 的提醒
ThreadLocal<T>
。
新的 ThreadLocal 类为我们提供了强类型、 我们可以使用本地范围的对象来设置保持独立的数据 对于每个线程。这允许我们使用每个线程存储的数据, 无需在我们的类型中引入静态变量。 在内部,ThreadLocal 实例会自动设置 静态数据,管理其生命周期,进行所有的转换 我们的具体类型。这使得开发变得更加简单。
// Demonstrates:
// ThreadLocal(T) constructor
// ThreadLocal(T).Value
// One usage of ThreadLocal(T)
static void Main()
{
// Thread-Local variable that yields a name for a thread
ThreadLocal<string> ThreadName = new ThreadLocal<string>(() =>
{
return "Thread" + Thread.CurrentThread.ManagedThreadId;
});
// Action that prints out ThreadName for the current thread
Action action = () =>
{
// If ThreadName.IsValueCreated is true, it means that we are not the
// first action to run on this thread.
bool repeat = ThreadName.IsValueCreated;
Console.WriteLine("ThreadName = {0} {1}", ThreadName.Value, repeat ? "(repeat)" : "");
};
// Launch eight of them. On 4 cores or less, you should see some repeat ThreadNames
Parallel.Invoke(action, action, action, action, action, action, action, action);
// Dispose when you are done
ThreadName.Dispose();
}
所以你的代码会像这样:
ThreadLocal<Random> ThreadName = new ThreadLocal<Random>(() =>
{
return new Random();
});
var options = new ExecutionDataflowBlockOptions
{
MaxDegreeOfParallelism = 4,
EnsureOrdered = false,
BoundedCapacity = 4 * 8
};
var actionBlock = new ActionBlock<int>(async request =>
{
bool repeat = ThreadName.IsValueCreated;
var random = ThreadName.Value; // your local random class
Console.WriteLine($"Thread: {Thread.CurrentThread.ManagedThreadId},
repeat: ", repeat ? "(repeat)" : "");
}, options);