Part 94 - Difference between Monitor and lock in C#

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Part 93 - Protecting shared resources from concurrent access in multithreading



In this video we will discuss, the Difference between Monitor class and lock.



Both Monitor class and lock provides a mechanism that synchronizes access to objects. lock is the shortcut for Monitor.Enter with try and finally.

This means that, the following code 

static object _lock = new object();

public static void AddOneMillion()

{

    for (int i = 1; i <= 1000000; i++)

    {

        lock (_lock)

        {

            Total++;

        }

    }

}

can be rewritten as shown below:

static object _lock = new object();

public static void AddOneMillion()

{

    for (int i = 1; i <= 1000000; i++)

    {

        // Acquires the exclusive lock

        Monitor.Enter(_lock);

        try

        {

            Total++;

        }

        finally

        {

            // Releases the exclusive lock

            Monitor.Exit(_lock);

        }

    }

}

In C# 4, it is implement slightly differently as shown below

static object _lock = new object();

public static void AddOneMillion()

{

    for (int i = 1; i <= 1000000; i++)

    {

        bool lockTaken = false;

        // Acquires the exclusive lock

        Monitor.Enter(_lock, ref lockTaken);

        try

        {

            Total++;

        }

        finally

        {

            // Releases the exclusive lock

            if (lockTaken)

                Monitor.Exit(_lock);

        }

    }

}

So, in short, lock is a shortcut and it's the option for the basic usage. If you need more control to implement advanced multithreading solutions using TryEnter() Wait(), Pulse(), & PulseAll() methods, then the Monitor class is your option.