c# - What is better? Static methods OR Instance methods

Question

I found that there are two type of methods called static methods and instance methods and their differences. But still I couldnt understand the advantages of one over another.

Sometimes i feel that static methods are not 100% object oriented.

Are there any performance differences between this two.

Can someone help?

Answer 1

In a perfect OO world there probably wouldn't be any need for static methods (I think Eiffel doesn't have them, either). But at the end of the day what matters is not OO-pureness of your code (C# has enough concepts that aren't strictly pure OO, like extension methods, for example) but rather what you're getting done.

You can use static methods for general helper methods (that don't need a general helper class or state on their own) or things like Color.FromARGB() which behave slightly contructor-like for value types.

In general, any method that doesn't touch an objects state (and therefore is more class-specific than object-specific) can be made static. Performance differences shouldn't really arise. Not very measurable, in any case. Jan Gray's great article Writing faster managed code: Know what things cost has some hard data on this, albeit to be taken with care.