好吧，我可以解決我的問題看單聲道項目。
// SemaphoreSlim.cs
//
// Copyright (c) 2008 Jérémie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//
using System;
using System.Diagnostics;
using System.Threading.Tasks;
namespace System.Threading
{
public class SemaphoreSlimCustom : IDisposable
{
const int spinCount = 10;
const int deepSleepTime = 20;
private object _sync = new object();
int maxCount;
int currCount;
bool isDisposed;
public int MaxCount
{
get { lock (_sync) { return maxCount; } }
set
{
lock (_sync)
{
maxCount = value;
}
}
}
EventWaitHandle handle;
public SemaphoreSlimCustom (int initialCount) : this (initialCount, int.MaxValue)
{
}
public SemaphoreSlimCustom (int initialCount, int maxCount)
{
if (initialCount < 0 || initialCount > maxCount || maxCount < 0)
throw new ArgumentOutOfRangeException ("The initialCount argument is negative, initialCount is greater than maxCount, or maxCount is not positive.");
this.maxCount = maxCount;
this.currCount = initialCount;
this.handle = new ManualResetEvent (initialCount > 0);
}
public void Dispose()
{
Dispose(true);
}
protected virtual void Dispose (bool disposing)
{
isDisposed = true;
}
void CheckState()
{
if (isDisposed)
throw new ObjectDisposedException ("The SemaphoreSlim has been disposed.");
}
public int CurrentCount {
get {
return currCount;
}
}
public int Release()
{
return Release(1);
}
public int Release (int releaseCount)
{
CheckState();
if (releaseCount < 1)
throw new ArgumentOutOfRangeException ("releaseCount", "releaseCount is less than 1");
// As we have to take care of the max limit we resort to CAS
int oldValue, newValue;
do {
oldValue = currCount;
newValue = (currCount + releaseCount);
newValue = newValue > maxCount ? maxCount : newValue;
} while (Interlocked.CompareExchange (ref currCount, newValue, oldValue) != oldValue);
handle.Set();
return oldValue;
}
public void Wait()
{
Wait (CancellationToken.None);
}
public bool Wait (TimeSpan timeout)
{
return Wait ((int)timeout.TotalMilliseconds, CancellationToken.None);
}
public bool Wait (int millisecondsTimeout)
{
return Wait (millisecondsTimeout, CancellationToken.None);
}
public void Wait (CancellationToken cancellationToken)
{
Wait (-1, cancellationToken);
}
public bool Wait (TimeSpan timeout, CancellationToken cancellationToken)
{
CheckState();
return Wait ((int)timeout.TotalMilliseconds, cancellationToken);
}
public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
{
CheckState();
if (millisecondsTimeout < -1)
throw new ArgumentOutOfRangeException ("millisecondsTimeout",
"millisecondsTimeout is a negative number other than -1");
Stopwatch sw = Stopwatch.StartNew();
Func<bool> stopCondition =() => millisecondsTimeout >= 0 && sw.ElapsedMilliseconds > millisecondsTimeout;
do {
bool shouldWait;
int result;
do {
cancellationToken.ThrowIfCancellationRequested();
if (stopCondition())
return false;
shouldWait = true;
result = currCount;
if (result > 0)
shouldWait = false;
else
break;
} while (Interlocked.CompareExchange (ref currCount, result - 1, result) != result);
if (!shouldWait) {
if (result == 1)
handle.Reset();
break;
}
SpinWait wait = new SpinWait();
while (Thread.VolatileRead (ref currCount) <= 0) {
cancellationToken.ThrowIfCancellationRequested();
if (stopCondition())
return false;
if (wait.Count > spinCount) {
int diff = millisecondsTimeout - (int)sw.ElapsedMilliseconds;
int timeout = millisecondsTimeout < 0 ? deepSleepTime :
Math.Min (Math.Max (diff, 1), deepSleepTime);
handle.WaitOne (timeout);
} else
wait.SpinOnce();
}
} while (true);
return true;
}
public WaitHandle AvailableWaitHandle {
get {
return handle;
}
}
public Task WaitAsync()
{
return Task.Factory.StartNew (() => Wait());
}
public Task WaitAsync (CancellationToken cancellationToken)
{
return Task.Factory.StartNew (() => Wait (cancellationToken), cancellationToken);
}
public Task<bool> WaitAsync (int millisecondsTimeout)
{
return Task.Factory.StartNew (() => Wait (millisecondsTimeout));
}
public Task<bool> WaitAsync (TimeSpan timeout)
{
return Task.Factory.StartNew (() => Wait (timeout));
}
public Task<bool> WaitAsync (int millisecondsTimeout, CancellationToken cancellationToken)
{
return Task.Factory.StartNew (() => Wait (millisecondsTimeout, cancellationToken), cancellationToken);
}
public Task<bool> WaitAsync (TimeSpan timeout, CancellationToken cancellationToken)
{
return Task.Factory.StartNew (() => Wait (timeout, cancellationToken), cancellationToken);
}
}
}
或者只是調用構造函數：http://msdn.microsoft.com/en-us/library/dd270891(v=vs.110).aspx –
即使我自己的類，它封裝SemaphoreSlim，我需要靈活地將最大併發呼叫切換爲上或下。即從1000開始，改爲600，並在一段時間後改爲1700. –
@JimMischel當然，儘管如果你想真的能夠改變適當的最大值，你真的需要用另一種類型來組合它，這樣你才能確保當它已經達到最大值時釋放它，而不增加最大值就成爲一個noop（或一個例外）。 – Servy