In my ASP.net project I need to validate some basic data types for user inputs. The data types are like numeric, decimal, datetime etc.
What is the best approach that I should have taken in terms of performance? Is it to do it by Regex.IsMatch()
or by TryParse()
?
Thanks in advance.
As other would say, the best way to answer that is to measure it ;)
Don't try to make regexes do everything.
Sometimes a simple regex will get you 90% of the way and to make it do everything you need the complexity grows ten times or more.
Then I often find that the simplest solution is to use the regex to check the form and then rely on good old code for the value checking.
Take a date for example, use a regex to check for a match on a date format and then use capturing groups to check the values of the individual values.
I'd guess TryParse is quicker, but more importantly, it's more expressive.
The regular expressions can get pretty ugly when you consider all the valid values for each data type you're using. For example, with DateTime you have to ensure the month is between 1 and 12, and that the day is within the valid range for that particular month.
TryParse
andRegex.IsMatch
are used for two fundamentally different things.Regex.IsMatch
tells you if the string in question matches some particular pattern. It returns a yes/no answer.TryParse
actually converts the value if possible, and tells you whether it succeeded.Unless you're very careful in crafting the regular expression,
Regex.IsMatch
can returntrue
whenTryParse
will returnfalse
. For example, consider the simple case of parsing abyte
. WithTryParse
you have:If the value in
myString
is between 0 and 255,TryParse
will returntrue
.Now, let's try with
Regex.IsMatch
. Let's see, what should that regular expression be? We can't just say@"\d+"
or even@\d{1,3}"
. Specifying the format becomes a very difficult job. You have to handle leading 0s, leading and trailing white space, and allow255
but not256
.And that's just for parsing a 3-digit number. The rules get even more complicated when you're parsing an
int
orlong
.Regular expressions are great for determining form. They suck when it comes to determining value. Since our standard data types all have limits, determining its value is part of figuring out whether or not the number is valid.
You're better off using
TryParse
whenever possible, if only to save yourself the headache of trying to come up with a reliable regular expression that will do the validation. It's likely (I'd say almost certain) that a particularTryParse
for any of the native types will execute faster than the equivalent regular expression.The above said, I've probably spent more time on this answer than your Web page will spend executing your
TryParse
orRegex.IsMatch
--total throughout its entire life. The time to execute these things is so small in the context of everything else your Web site is doing, any time you spend pondering the problem is wasted.Use
TryParse
if you can, because it's easier. Otherwise useRegex
.