asked on

Difference between [MethodImpl(MethodImplOptions.Synchronized)] and lock(this)

I was searching for a C# counterpart for the Java "synchronized" keyword and I found that there is an Attribute "[MethodImpl(MethodImplOptions.Synchronized)]".
There are quite a lot of synchronization attributes in C# which is rather confusing.

What is the difference between:

public void MyMethod()
{
lock(this)
{
...
}
}

and this:

[MethodImpl(MethodImplOptions.Synchronized)]
public void MyMethod()
{
...
}

SOLUTION

TheAvenger

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

ptmcomp

ASKER

Ok so [MethodImpl(MethodImplOptions.Synchronized)] does the same as the code below?

private static object myMethodLockRoot = new object();
public void MyMethod()
{
lock(myMethodLockRoot)
{
...
}
}

TheAvenger

if you use the myMethodLockRoot object only for this, yes

ptmcomp

ASKER

If I translate this Java code:

public synchronized void myMethod() {
....
}

Shall I use the Attribute or an explicit lock?

PS: @TheAvenger: I'll give you the points but I don't want to close the question yet, I will raise the points and split them if I get more input about differences in IL-Code or other background information.

_TAD_

** Not for points **

I think Avenger has pretty much nailed it right on the head. It really comes down to locking an object or a method (more or less).

If the object exists ONLY inside of a single method pretty much either code does the exact same thing.

In your particular case

<Java>
public synchronized void myMethod() {
....
}

You'll want to use the attribute method of synchronizing.

ASKER CERTIFIED SOLUTION

_TAD_

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

TheAvenger

Can't add anything more to _TAD_: said all

ptmcomp

ASKER

Ok guys, thanks a lot!

ptmcomp

ASKER

Weird! - How does EE determine which is the "accepted" and which is the "assisted" answer?? Anyway it was meant to be other way around and the points should be 250 for TheAvenger and 100 for _TAD_ both with grade A.

TheAvenger

The grade is A and I got 1000 points (4 x 250) so I think only the remarks here are wrong....

ptmcomp

ASKER

Just had a look at my Java book it says synchronize locks "this" which would mean:

<JAVA>
public synchronized void myMethod() {
....
}
-- Same as --

<C#>
public void MyMethod()
{
lock(this)
{
...
}
}

Anyway I think I won't use the Attribute since it's harder to understand.

mjwills

TheAvenger,

<quote>
MethodImplOptions.Synchronized: Specifies the method can be executed by only one thread at a time.

The lock keyword marks a statement block as a critical section by obtaining the mutual-exclusion lock for a given object, executing a statement, and then releasing the lock

So: if you lock an object, all other threads that need to access THIS PARTICULAR OBJECT will wait, until the other object finishes. However if you mark a method as Synchronized, THIS PARTICULAR METHOD will not be executed at more than one thread. Lock secures the object, Synchronized secures the method
</quote>

Incorrect. Both lock(this) and MethodImplOptions.Synchronized do the same thing - they lock against the object. This is why MethodImplOptions.Synchronized should be avoided. See http://www.dotnet247.com/247reference/msgs/45/225597.aspx (for example).

Seeya
Matthew

ptmcomp

ASKER

Thanks for the hint. I think I'll stick to the explicit locks since I know what they do and don't change behaviour in further versions.