Interlocked.Increment Method (Int32%)
Updated: February 2009
Increments a specified variable and stores the result, as an atomic operation.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- location
- Type: System.Int32%
The variable whose value is to be incremented.
| Exception | Condition |
|---|---|
| NullReferenceException | The address of location is a null pointer. |
This method handles an overflow condition by wrapping: if location = Int32.MaxValue, location + 1 = Int32.MinValue. No exception is thrown.
The following code example shows a thread-safe way to increment and decrement an integer value. SafeInstanceCount will always be zero. However, UnsafeInstanceCount will not necessarily be zero because a race condition occurs between incrementing and decrementing the count. This effect is especially marked on a multiprocessor computer.
using System; using System.Threading; class Test { static void Main() { Thread thread1 = new Thread(new ThreadStart(ThreadMethod)); Thread thread2 = new Thread(new ThreadStart(ThreadMethod)); thread1.Start(); thread2.Start(); thread1.Join(); thread2.Join(); // Have the garbage collector run the finalizer for each // instance of CountClass and wait for it to finish. GC.Collect(); GC.WaitForPendingFinalizers(); Console.WriteLine("UnsafeInstanceCount: {0}" + "\nSafeCountInstances: {1}", CountClass.UnsafeInstanceCount.ToString(), CountClass.SafeInstanceCount.ToString()); } static void ThreadMethod() { CountClass cClass; // Create 100,000 instances of CountClass. for(int i = 0; i < 100000; i++) { cClass = new CountClass(); } } } class CountClass { static int unsafeInstanceCount = 0; static int safeInstanceCount = 0; static public int UnsafeInstanceCount { get {return unsafeInstanceCount;} } static public int SafeInstanceCount { get {return safeInstanceCount;} } public CountClass() { unsafeInstanceCount++; Interlocked.Increment(ref safeInstanceCount); } ~CountClass() { unsafeInstanceCount--; Interlocked.Decrement(ref safeInstanceCount); } }
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.