[MethodImpl(MethodImplOptions.Synchronized)]

　　在NopCommerce项目的Nop.Core类库中有一个EngineContext类中有一个Initialize方法用到了[MethodImpl(MethodImplOptions.Synchronized)]

/// <summary>
/// Initializes a static instance of the Nop factory.
/// </summary>
/// <param name="forceRecreate">Creates a new factory instance even though the factory has been previously initialized.</param>
[MethodImpl(MethodImplOptions.Synchronized)]
public static IEngine Initialize(bool forceRecreate)
{
if (Singleton<IEngine>.Instance == null || forceRecreate)
{
var config = ConfigurationManager.GetSection("NopConfig") as NopConfig;
Singleton<IEngine>.Instance = CreateEngineInstance(config);
Singleton<IEngine>.Instance.Initialize(config);
}
return Singleton<IEngine>.Instance;
}

我的理解它和Lock差不多，是解决多线程同步问题的；

该方法一次只能由一个线程执行。 静态方法锁定类型，而实例方法锁定实例。 在任何实例函数中只能执行一个线程，并且在类的任何静态函数中只能执行一个线程。

如果[MethodImplAttribute(MethodImplOptions.Synchronized)]被应用到instance method，相当于对当前实例加锁。

如果[MethodImplAttribute(MethodImplOptions.Synchronized)]被应用到static method，相当于当前类型加锁。

实例方法锁定实例

class Program
{
　　　　//在入口Main方法中，创建SyncHelper对象，通过一个System.Threading.Timer对象实现每隔1s调用该对象的Execute方法：
static void Main(string[] args)
{
SyncHelper sync = new SyncHelper();
Timer timer = new Timer(delegate
{
sync.Execute();
}, null, 0, 1000);

Console.ReadKey();
}
}

class SyncHelper
{
public void Execute()
{
Console.WriteLine("Excute at {0}", DateTime.Now);
Thread.Sleep(5000);
}
}

class Program
{
static void Main(string[] args)
{
SyncHelper sync = new SyncHelper();
Timer timer = new Timer(delegate
{
sync.Execute();
}, null, 0, 1000);

Console.ReadKey();
}
}

class SyncHelper
{
[MethodImpl(MethodImplOptions.Synchronized)]
public void Execute()
{
Console.WriteLine("Excute at {0}", DateTime.Now);
Thread.Sleep(5000);
}
}

静态方法锁定类型

class Program
{
static void Main(string[] args)
{
SyncHelper sync = new SyncHelper();
Timer timer = new Timer(delegate
{
SyncHelper.Execute();
}, null, 0, 1000);

Console.ReadKey();
}
}

class SyncHelper
{
[MethodImpl(MethodImplOptions.Synchronized)]
public static void Execute()
{
Console.WriteLine("Excute at {0}", DateTime.Now);
Thread.Sleep(5000);
}
}

例子：http://www.cnblogs.com/artech/archive/2008/10/17/1313209.html