Does c# have its own version of the java "synchronized" keyword?
I.e. in java it can be specified either to a function, an object or a block of code, like so:
public synchronized void doImportantStuff() {
// dangerous code goes here.
}
or
public void doImportantStuff() {
// trivial stuff
synchronized(someLock) {
// dangerous code goes here.
}
}
First - most classes will never need to be thread-safe. Use YAGNI: only apply thread-safety when you know you actually are going to use it (and test it).
For the method-level stuff, there is [MethodImpl]
:
[MethodImpl(MethodImplOptions.Synchronized)]
public void SomeMethod() {/* code */}
This can also be used on accessors (properties and events):
private int i;
public int SomeProperty
{
[MethodImpl(MethodImplOptions.Synchronized)]
get { return i; }
[MethodImpl(MethodImplOptions.Synchronized)]
set { i = value; }
}
Note that field-like events are synchronized by default, while auto-implemented properties are not:
public int SomeProperty {get;set;} // not synchronized
public event EventHandler SomeEvent; // synchronized
Personally, I don't like the implementation of MethodImpl
as it locks this
or typeof(Foo)
- which is against best practice. The preferred option is to use your own locks:
private readonly object syncLock = new object();
public void SomeMethod() {
lock(syncLock) { /* code */ }
}
Note that for field-like events, the locking implementation is dependent on the compiler; in older Microsoft compilers it is a lock(this)
/ lock(Type)
- however, in more recent compilers it uses Interlocked
updates - so thread-safe without the nasty parts.
This allows more granular usage, and allows use of Monitor.Wait
/Monitor.Pulse
etc to communicate between threads.
A related blog entry (later revisited).