Question

I’m trying to call the getter of a static variable in another class. Can someone tell me why this works:

protected static SymTab _symTab;

public SymTab symTab
{
    get{return _symTab;}
    set{_symTab = value;}
}

and this does not:

public static SymTab symTab {get; protected set;}

Answer 1

The first version has an instance property which gets/sets a static variable.

The second version has a static property which gets/sets a static variable. (The setter is protected, too, but that doesn’t seem to be your immediate problem.)

I would strongly discourage the first form – instance properties should reflect something about that instance; you wouldn’t expect setting a property on one instance to change the property value for a different instance.

With the second form, you can just use:

SymTab currentTab = TypeName.symTab;

instead of:

SymTab currentTab = someVariable.symTab;

Additionally, I would note:

• The property name symTab violates .NET naming conventions
• The type name SymTab isn’t as clear as SymbolTable or whatever that abbreviation is short for
• Mutable static variables are almost always a bad idea.

EDIT: Note that now we know it’s coming from Java, that explains the problem you’re seeing. In Java, it’s legal (but a bad idea) to refer to a static member “via” a variable or other expression. It makes for very confusing code though. For example:

Thread backgroundThread = new Thread(someRunnable);
backgroundThread.start();
backgroundThread.sleep(1000);

That makes it look like you’re telling the new thread to sleep, but actually it’s a call to the static Thread.sleep method which causes the current thread to sleep. Some Java IDEs will optionally flag this up as a warning or error.

Fortunately, C# doesn’t allow this in the first place.