Miscellaneous Performance

Question

Is it faster to make a comparison or a cast in C#.Net?
For example:

bool? flag = null;    
...    
if(flag == true)... or if((bool)flag)...  

Also, what is the cost (in memory) of a cast?

Answer 1

If memory serves the compiler will force you to cast the bool? to a bool before using it in the if statement. You might like the null coalesce operator:

//If flag == null then return false, otherwise return the value of flag.
if (flag ?? false)

Answer 2

IIRC, Those translate to roughly the same thing. Unless you're doing an absurdly large number of such checks, the difference is unnoticable for any practical purposes.

Answer 3

If a null value in flag means "false" I would use the comparison. The cast is a bad idea, beacuse it will throw an exception if flag is null. To be save you have to test for null before the cast. That means you have to do a comparion and a cast instead of a comparion only.

Answer 4

The performance difference is negligible.

Also keep in mind that

bool? flag = null;
// ...other code...
if ((bool)flag)
{
}

might throw an InvalidOperationException if flag was not assigned in the code between the variable declaration and the cast.