Finding lines NOT containing certain words – RegEx magic


Regular expressions are full of surprises. Just when you thought you’ve seen it all, out comes a “what if I want to do this, but also that and match these but not those” - and the worse thing is that it is usually my idea in the first place!

So here’s an interesting one: While working on the FxCop reports for our product, I wanted to find (and eventually replace) all public members in the code.
My first thought was this:

public.*;$

But this expression brought back thousands of false-positives like delegates, events, read-only fields, constants, etc. which are perfectly legal, even under the strict rules of FxCop. I needed something that would filter out the lines that contain certain keywords.

After rummaging the MSDN page for regular expressions and some trial and error I found that the following regular expression did the trick quite nicely, while keeping a good false-positive ratio:

public ~(const|event|delegate|readonly|static readonly|static extern|abstract).*;$

In English: look for lines with the word public, not followed by any of the words const, event, delegate, etc. and that end with ';'

The rarely used  ~() syntax allows for specifying words that will break the match if found in the specified location.

You can also modify the above RegEx to support replacing the faulty line with auto-implemented properties (new in .NET 3.0).

{public ~(const|event|delegate|readonly|static readonly|static extern|abstract).*};$ 

And use the following string in the “Replace with” field to make an auto-implemented property:

\1 { get; set; }

A word of warning: Do not run a solution-wide find-replace using this method, as you might break things without noticing. Hand-pick your changes!

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