In our old code I'vew noticed a few examples of code like the following:

 MyFortune = Decimal.Add(MyFortune, .01m);

I was wandered, why they didn't use "+" sign, and didn't find any explanation.
The MSDN reference documentation doesn't explain, that methods like Add, Subtract,Multiply,Divide usually should not be called explicitely. 

Instead of using Add method it's simpler to use + sign ( Addition Operator ).
E.g.
    MyFortune = Decimal.Add(MyFortune, .01m);
can be rewritten as 
    MyFortune += .01m;