1..net2.0支持方法
来自：官方例子
// This example shows a ReaderWriterLock protecting a shared // resource that is read concurrently and written exclusively // by multiple threads. // The complete code is located in the ReaderWriterLock // class topic. using System; using System.Threading; public class Test { // Declaring the ReaderWriterLock at the class level // makes it visible to all threads. static ReaderWriterLock rwl = new ReaderWriterLock(); // For this example, the shared resource protected by the // ReaderWriterLock is just an integer. static int resource = 0; const int numThreads = 26; static bool running = true; static Random rnd = new Random(); // Statistics. static int readerTimeouts = 0; static int writerTimeouts = 0; static int reads = 0; static int writes = 0; public static void Main(string[] args) { // Start a series of threads. Each thread randomly // performs reads and writes on the shared resource. Thread[] t = new Thread[numThreads]; for (int i = 0; i < numThreads; i++) { t[i] = new Thread(new ThreadStart(ThreadProc)); t[i].Name = new String(Convert.ToChar(i + 65), 1); t[i].Start(); if (i > 10) Thread.Sleep(300); } // Tell the threads to shut down, then wait until they all // finish. running = false; for (int i = 0; i < numThreads; i++) { t[i].Join(); } // Display statistics. Console.WriteLine("\r\n{0} reads, {1} writes, {2} reader time-outs, {3} writer time-outs.", reads, writes, readerTimeouts, writerTimeouts); Console.WriteLine("Press ENTER to exit."); Console.ReadLine(); } static void ThreadProc() { // As long as a thread runs, it randomly selects // various ways to read and write from the shared // resource. Each of the methods demonstrates one // or more features of ReaderWriterLock. while (running) { double action = rnd.NextDouble(); if (action < .8) ReadFromResource(10); else if (action < .81) ReleaseRestore(50); else if (action < .90) UpgradeDowngrade(100); else WriteToResource(100); } } // Shows how to request and release a reader lock, and // how to handle time-outs. static void ReadFromResource(int timeOut) { try { rwl.AcquireReaderLock(timeOut); try { // It is safe for this thread to read from // the shared resource. Display("reads resource value " + resource); Interlocked.Increment(ref reads); } finally { // Ensure that the lock is released. rwl.ReleaseReaderLock(); } } catch (ApplicationException) { // The reader lock request timed out. Interlocked.Increment(ref readerTimeouts); } } // Shows how to request and release the writer lock, and // how to handle time-outs. static void WriteToResource(int timeOut) { try { rwl.AcquireWriterLock(timeOut); try { // It is safe for this thread to read or write // from the shared resource. resource = rnd.Next(500); Display("writes resource value " + resource); Interlocked.Increment(ref writes); } finally { // Ensure that the lock is released. rwl.ReleaseWriterLock(); } } catch (ApplicationException) { // The writer lock request timed out. Interlocked.Increment(ref writerTimeouts); } } // Shows how to request a reader lock, upgrade the // reader lock to the writer lock, and downgrade to a // reader lock again. static void UpgradeDowngrade(int timeOut) { try { rwl.AcquireReaderLock(timeOut); try { // It is safe for this thread to read from // the shared resource. Display("reads resource value " + resource); Interlocked.Increment(ref reads); // If it is necessary to write to the resource, // you must either release the reader lock and // then request the writer lock, or upgrade the // reader lock. Note that upgrading the reader lock // puts the thread in the write queue, behind any // other threads that might be waiting for the // writer lock. try { LockCookie lc = rwl.UpgradeToWriterLock(timeOut); try { // It is safe for this thread to read or write // from the shared resource. resource = rnd.Next(500); Display("writes resource value " + resource); Interlocked.Increment(ref writes); } finally { // Ensure that the lock is released. rwl.DowngradeFromWriterLock(ref lc); } } catch (ApplicationException) { // The upgrade request timed out. Interlocked.Increment(ref writerTimeouts); } // When the lock has been downgraded, it is // still safe to read from the resource. Display("reads resource value " + resource); Interlocked.Increment(ref reads); } finally { // Ensure that the lock is released. rwl.ReleaseReaderLock(); } } catch (ApplicationException) { // The reader lock request timed out. Interlocked.Increment(ref readerTimeouts); } } // Shows how to release all locks and later restore // the lock state. Shows how to use sequence numbers // to determine whether another thread has obtained // a writer lock since this thread last accessed the // resource. static void ReleaseRestore(int timeOut) { int lastWriter; try { rwl.AcquireReaderLock(timeOut); try { // It is safe for this thread to read from // the shared resource. Cache the value. (You // might do this if reading the resource is // an expensive operation.) int resourceValue = resource; Display("reads resource value " + resourceValue); Interlocked.Increment(ref reads); // Save the current writer sequence number. lastWriter = rwl.WriterSeqNum; // Release the lock, and save a cookie so the // lock can be restored later. LockCookie lc = rwl.ReleaseLock(); // Wait for a random interval (up to a // quarter of a second), and then restore // the previous state of the lock. Note that // there is no time-out on the Restore method. Thread.Sleep(rnd.Next(250)); rwl.RestoreLock(ref lc); // Check whether other threads obtained the // writer lock in the interval. If not, then // the cached value of the resource is still // valid. if (rwl.AnyWritersSince(lastWriter)) { resourceValue = resource; Interlocked.Increment(ref reads); Display("resource has changed " + resourceValue); } else { Display("resource has not changed " + resourceValue); } } finally { // Ensure that the lock is released. rwl.ReleaseReaderLock(); } } catch (ApplicationException) { // The reader lock request timed out. Interlocked.Increment(ref readerTimeouts); } } // Helper method briefly displays the most recent // thread action. Comment out calls to Display to // get a better idea of throughput. static void Display(string msg) { Console.Write("Thread {0} {1}. \r", Thread.CurrentThread.Name, msg); } }
2..net 3.5支持方法
来自：https://www.cnblogs.com/Tench/p/6159763.html
class Program{
static int LogCount = 100;
static int WritedCount = 0;
static int FailedCount = 0;
static void Main(string[] args)
{
//迭代运行写入日志记录
Parallel.For(0, LogCount, e =>
{
WriteLog();
});
Console.WriteLine(string.Format("\r\nLog Count:{0}.\t\tWrited Count:{1}.\tFailed Count:{2}.", LogCount.ToString(), WritedCount.ToString(), FailedCount.ToString()));
Console.Read();
}
//读写锁，当资源处于写入模式时，其他线程写入需要等待本次写入结束之后才能继续写入
static ReaderWriterLockSlim LogWriteLock = new ReaderWriterLockSlim();
static void WriteLog()
{
try
{
//设置读写锁为写入模式独占资源，其他写入请求需要等待本次写入结束之后才能继续写入
//注意：长时间持有读线程锁或写线程锁会使其他线程发生饥饿 (starve)。 为了得到最好的性能，需要考虑重新构造应用程序以将写访问的持续时间减少到最小。
// 从性能方面考虑，请求进入写入模式应该紧跟文件操作之前，在此处进入写入模式仅是为了降低代码复杂度
// 因进入与退出写入模式应在同一个try finally语句块内，所以在请求进入写入模式之前不能触发异常，否则释放次数大于请求次数将会触发异常
LogWriteLock.EnterWriteLock();
var logFilePath = "log.txt";
var now = DateTime.Now;
var logContent = string.Format("Tid: {0}{1} {2}.{3}\r\n", Thread.CurrentThread.ManagedThreadId.ToString().PadRight(4), now.ToLongDateString(), now.ToLongTimeString(), now.Millisecond.ToString());
File.AppendAllText(logFilePath, logContent);
WritedCount++;
}
catch (Exception)
{
FailedCount++;
}
finally
{
//退出写入模式，释放资源占用
//注意：一次请求对应一次释放
// 若释放次数大于请求次数将会触发异常[写入锁定未经保持即被释放]
// 若请求处理完成后未释放将会触发异常[此模式不下允许以递归方式获取写入锁定]
LogWriteLock.ExitWriteLock();
}
}
}