Best way to check if a string is empty

[Mutant_Fruit]

We should agree that it boils down to the personal inclination of a developer or organization, some would prefer performance over readability and readable for some can be not that readable to others, do you agree?

Except that in either case, 'performance' doesn't come into it. It's another premature optimisation If you're worried about performance differences between String.IsNullOrEmpty and string.Length == 0, you're worrying about completely the wrong things. What you should be worried about is whether or not you want to allow a null or empty string. If you don't, you should use String.IsNullOrEmpty.

Of course, the source of your string should be part of your 'view', which should be completely disconnected from your model and controller (MVC pattern), so your model will be doing all the validation, which means you can't rely on the source of your data being a TextBox, which means you can't rely on it being non-null.

Finally, near in mind that you validate before you store. Validation will done a hell of a lot less than the variable will be used, so even if you do 'mega optimise' your validation methods you're not going to get a real world performance boost.