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I am sure everybody has had his/her share of regex woes.

We have a big application with around 30 developers working on a mvc3 web application , and the two fold regex validations (front-end and server side) is becoming a nightmare to maintain.

Is there a way to keep all the regexes in one place ? so that they can be used as attributes for entities and also be used for validations in the controller?

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Could you maybe copy or generate both from a single source automatically during build? – Péter Török Nov 22 '11 at 12:07
could you elaborate a bit more ? – Shekhar Nov 22 '11 at 12:49
My idea was, since it would be awkward to generate / reuse client side code from server side code, or vice versa, maybe it would be simpler to generate both from a third source. You could store the regexes in a plain text file, a DB, ... then generate the client and server side sources during the build from the stored regex data. Since I have no idea how the regexes are contained in your source code currently, I can't be more concrete than this. – Péter Török Nov 22 '11 at 13:21
up vote 1 down vote accepted

What are you using for validation now? Generally, the default, built-in DataAnnotations do just what you are describing. Another option is FluentValidation which also works with client-side validation.

In any case this is a solved problem in general.

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You could store the regexes in a table in your database, with a name a the key and then the two variants for front-end and back-end use, soemthing like:

regex_name | front_end                       | back end
post_code  |"[a-zA-Z]\d[a-zA-Z] \d[a-zA-Z]\d"|"[a-zA-Z]\d[a-zA-Z] \d[a-zA-Z]\d"

Of course, putting this in the database could make things difficult if you need a regex before you're connected to the database (probably won't happen in this case, but you never know) so you could implement a similar idea with a static class that just has a dictionary of names and the text for the regex versions.

Or you could store this in a CSV file and then load it into a cache at application startup. There are many ways to do this, I'm not sure what is the best for your team.

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My suggestion as well. I've done this with a database as well as in a XML file. – jfrankcarr Nov 22 '11 at 14:45

you are talking about shared regex`s for JavaScript (ECMA) and C# (NET) correct? this is not possible because .NET and ECMA use different flavors, see Regular Expression Flavor Comparison for more info.

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You can put the regex strings in your web config and call they dynamically in your page and your code. In this manner the strings will exist in a single location, will be able to be modified with out requiring a recompile, and will be available to your code through out your application.

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