Why is lock much slower than Monitor.TryEnter?

Question

Results

Lock: 85.3 microseconds

Monitor.TryEnter: 11.0 microseconds

Isn\'t the lock expanded into the same code?

Edit: Results with 1000 iteratio

Answer 1

You can use .NET reflector to inspect the generated IL. The lock keyword uses Monitor.Enter instead of Monitor.TryEnter - here's the short answer to your question. Here's how your code looks like when disassembled and translated back to C#:

public void Lock_Performance_Test()
{
    Stopwatch csLock = Stopwatch.StartNew();
    int i = 0;
    while (i < 100)
    {
        object CS$2$0000;
        bool <>s__LockTaken0 = false;
        try
        {
            Monitor.Enter(CS$2$0000 = this.object1, ref <>s__LockTaken0);
            i++;
        }
        finally
        {
            if (<>s__LockTaken0)
            {
                Monitor.Exit(CS$2$0000);
            }
        }
    }
    csLock.Stop();
    Stopwatch csMonitor = Stopwatch.StartNew();
    i = 0;
    while (i < 100)
    {
        if (Monitor.TryEnter(this.object1, TimeSpan.FromSeconds(10.0)))
        {
            try
            {
                i++;
            }
            finally
            {
                Monitor.Exit(this.object1);
            }
        }
    }
    csMonitor.Stop();
    Console.WriteLine("Lock: {0:f1} microseconds", csLock.Elapsed.Ticks / 10M);
    Console.WriteLine("Monitor.TryEnter: {0:f1} microseconds", csMonitor.Elapsed.Ticks / 10M);
}