>Did you step through your code with the debugger to see if the result was really 2? It might have been 1.8, and WriteLine *might* be rounding it without any additional formatting. (I don't use writeline for anything, just a guess). Just a hunch...

Sorry Kevin ; I encountered this behaviour inside a unit test, the writeline example was just for showing it here.
For more clarity I now added :

if (result==2M) Console.Out.WriteLine("Result is 2");
if (result==1.8M) Console.Out.WriteLine("Result is 1.8");

Result is 2.