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I am pretty new to multi-threading in general and I would like to know how can I lock a shared integer variable to not be accessed by other threads while it is read/updated by an other thread.

When I try do do SyncLock myInteger, I get that error : Error 6 'SyncLock' operand cannot be of type 'Integer' because 'Integer' is not a reference type.

Here a simplified example of what I mean

Private Shared myInteger As Integer

Private Sub MySub()
  SyncLock myInteger ' This does not work
    ' read/write a new value to myInteger
  End SyncLock
End Sub

MySub is called by multiple instances of the class, and running in multiple threads

MaxiWheat
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1 Answers1

9

I suspect you don't fully understand what SyncLock does. Even if you could do it (if Integer were a reference type, for example) you wouldn't want to do it - because when you replaced the value of myInteger, the lock would be useless.

You should either lock on something else (personally I generally declare a separate, read-only variable purely for the sake of locking, usually of type Object) or if you only want to operate on myInteger at any time (rather than some compound operation which needs to read or update several variables at the same time), use the Interlocked class.

Jon Skeet
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  • Your suspicions are right, I don't fully understand what SyncLock does ;-) But with your explanation that it could be any trivial Object, just to keep the lock, I think I get a better idea. Thank you SO Grand Master ;-) – MaxiWheat May 29 '12 at 17:10