Generic Threadsafe Property - multithreading

Question

I have created this "threadsafe" generic property, that i can use between the main thread and a background Thread. I made it because i was tired of creating Lock-Objects for all my properties and variables.
TLockedProp<MyType> = class
private
FMyProp:MyType;
PropLock:TObject;
procedure SetMyProp(const Value: MyType);
function GetMyProp: MyType;
published
property Value:MyType read GetMyProp write SetMyProp;
public
Constructor Create;
Destructor Destroy;override;
end;
{ TLockedProp<MyType> }
constructor TLockedProp<MyType>.Create;
begin
inherited;
PropLock:=TObject.create
end;
destructor TLockedProp<MyType>.Destroy;
begin
PropLock.Free;
inherited;
end;
function TLockedProp<MyType>.GetMyProp: MyType;
begin
TMonitor.Enter(PropLock);
result := FMyProp;
TMonitor.Exit(PropLock);
end;
procedure TLockedProp<MyType>.SetMyProp(const Value: MyType);
begin
TMonitor.Enter(PropLock);
FMyProp := Value;
TMonitor.Exit(PropLock);
end;
Are there any problems i am overlooking?
This is some code using this property class. Tell me what you think.
TBgThread=class(TThread)
private
FPaused: TLockedProp<boolean>;
FCount:TLockedProp<integer>;
procedure ChangeCount(pPlusMin:integer);
function GetPaused:boolean;
function GetCount:integer;
public
constructor Create;
destructor Destroy;override;
{Toggle Pause}
procedure PausePlay;
protected
procedure Execute;override;
published
Property Paused:boolean read GetPaused;
Property Count:integer read GetCount;
end;
constructor TBgThread.Create();
begin
inherited Create(true);;
FPaused:=TLockedProp<boolean>.create;
FPaused.Value:=false;
FCount:=TLockedProp<integer>.create;
FCount.Value:=0;
end;
destructor TBgThread.Destroy;
begin
FPaused.Free;
FCount.free;
inherited;
end;
procedure TBgThread.Execute;
begin
inherited;
Repeat
if not Paused then begin
Try
//do something
finally
ChangeCount(+1);
end;
end else
Sleep(90);
Until Terminated;
end;
function TBgThread.GetCount: integer;
begin
Result:=FCount.Value;
end;
procedure TBgThread.ChangeCount(pPlusMin: integer);
begin
FCount.Value:=FCount.Value+pPlusMin;
end;
function TBgThread.GetPaused: boolean;
begin
result := FPaused.Value;
end;
procedure TBgThread.PausePlay;
begin
FPaused.Value:=not FPaused.Value;
end;

Answer 1

Your code is fine and will serialize read/write access to the property. The only comment that I would make is that you do not need to create a separate lock object. You can remove PropLock and lock on Self instead.
I have an almost identical class in my code base. The only differences are:
I use a critical section rather than TMonitor because I still don't trust TMonitor. The early versions had a number of bugs and that dented my confidence. However, I suspect that the TMonitor code is most likely correct by now. So I see no reason for you to change.
I use try/finally with the code that locks and unlocks. This is perhaps a little pessimistic on my part, because it's hard to see how you could usefully recover from exceptions in the getter and setter methods. Force of habit I suppose.
FWIW, my version of your class looks like this:
type
TThreadsafe<T> = class
private
FLock: TCriticalSection;
FValue: T;
function GetValue: T;
procedure SetValue(const NewValue: T);
public
constructor Create;
destructor Destroy; override;
property Value: T read GetValue write SetValue;
end;
{ TThreadsafe<T> }
constructor TThreadsafe<T>.Create;
begin
inherited;
FLock := TCriticalSection.Create;
end;
destructor TThreadsafe<T>.Destroy;
begin
FLock.Free;
inherited;
end;
function TThreadsafe<T>.GetValue: T;
begin
FLock.Acquire;
Try
Result := FValue;
Finally
FLock.Release;
End;
end;
procedure TThreadsafe<T>.SetValue(const NewValue: T);
begin
FLock.Acquire;
Try
FValue := NewValue;
Finally
FLock.Release;
End;
end;
I guess there's really just one way to write this class!