Category Archives: Development

The Importance of knowing Regular Expressions

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It’s something that always mystifies me, it does seem that a lot of developers don’t know regular expression syntax very well. This came up when I was on some SharePoint 2013 training just before Christmas.

SharePoint 2013 introduces something called “Routing Rules”. These are rules that allow you to direct traffic to different front-end servers (or pools of servers), allowing you to isolate traffic, route to better health servers, etc.. Spence Harbar has a very good article about it.

Anyway, one some of the criteria that you can match rules on are Regular Expressions. However, SharePoint does warn you that Regex routing rules are slower – this is unsurprising. But how much slower than, say, a ‘Starts with’ or ‘Ends with’ rule? And on the Ignite training I did wonder about the efficiency of their example… Continue reading →

HTML 5 – Email Address Validation Regex

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And interesting one to stumble upon – the ‘official‘ regex for validating a email address:

Edit: I’ve had to break this down into parts – for some reason WordPress throws a 403 error if I don’t. I think it sees this regex as a security risk!

Before the @ sign:
^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+

The @ sign and after:
@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$

Reads like it should work pretty well to me. I didn’t realise before the @ was so generous. And you could shrink it by using a case insensitive operator.

Every Developer should know about Cryptography

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It fascinates me, but it seems like a lot of developers don’t know a lot about cryptography. Certainly, the litany of security bloopers caused by incorrectly implemented crypto makes it appear that way.

Encryption isn’t something that I work with every day, but as a web developer you can’t really get away from needing to secure something – and that means encryption.So, to overcome some of this it’s worth a bit of reading.

Bruce Schneier is a pretty interesting author. His books on Applied Cryptography and Practical Cryptography are excellent, and well worth a read for anyone starting to work with crypto. His blog is also an interesting discussion of security and risk in a wider context.

Troy Hunt has managed to write a number of posts that have grabbed my attention over the year or so. “Lessons in web site security anti-patterns” is just that, “A brief Sony password analysis” is fascinating, and “Our password hashing has no clothes” was eye opening. I like that his posts are strongly based on systematic analysis.

Cryptography on StackExchange can be interesting. It’s where I first heard of scrypt, which is quite interesting.

Anyway, I’ll try and update this if I find new, useful resources, or post your own favourites in the comments.

Lookbehinds, Regexes, and replacing \n

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This is a little note for myself; don’t forget lookbehinds (and lookaheads) in regular expressions as a way of matching text that you don’t want to replace.

For example, if converting new lines to carriage-return new-lines:

// \n ---> \r\n
string output = Regex.Replace(input, "(?<!\r)\n", "\r\n");

This pattern find any new line character ‘\n‘ and checks if the preceding character ‘(?< … )‘ is not a carriage return ‘!\r‘.

This is neater than my having a capture group for the preceding character, and then having to put that group into my replacement pattern.

TFS: Solution Explorer missing file status icons

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I’ve just had a bit of a problem with Solution Explorer in Visual Studio not showing the ‘checkout status’ icons from TFS – you know, the red tick, the padlock, etc.. These things:

I couldn’t figure out what was causing this, but found the solution on MSDN forums:

In VS 2010, while you have the solution open in Solution Explorer, select File-> Source Control-> Change Source Control, could you click on Bind for each project/solution? Binding provides version control functionality. This includes various version control icons that indicate status in Solution Explorer.

This advice was correct – I went to the binding dialog, and the solution and projects weren’t bound. I added the bindings back – and presto. I’m not sure, however, how the project became unbound…

 

Getting levels of the SharePoint Heirarchy and their Exceptions

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Something that I have to do time and again is get some element of SharePoint’s heirarchy, such as a site collection, site, list or item. This is pretty typical – that’s why we all use USING to ensure proper disposal of SPSites and SPWebs, right? But what happens if the thing you’re after isn’t there? What exception get’s thrown?

Well, this should be pretty clear:

try
{
    //FileNotFoundException if doesn't exist
    using (SPSite site = new SPSite(siteGuid))
    {
        //FileNotFoundException if doesn't exist
        using (SPWeb web = site.OpenWeb(webGuid))
        {
            //SPException if doesn't exist
            SPList list = web.Lists[listGuid];

            //ArgumentException if doesn't exist
            SPListItem item = list.GetItemByUniqueId(itemGuid);
        }
    }
}
catch (System.IO.FileNotFoundException fileEx2)
{
    // Site or Site Collection Not Found
}
catch (SPException spEx2)
{
    // List not found
}
catch (ArgumentException argEx2)
{
    // Item not found
}

Hopefully that might prove useful to someone – and a good reminder for me.

Make Visual Studio break on all Exceptions

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I’m a big fan of not raising exceptions if possible – rather than throwing and catching ‘expected exceptions’. To me, that phrase is an oxymoron – exceptions should be, um, exceptional, and it can make the wood hard to see for the trees when looking for proper exceptions.

Anyway, that aside – you can make Visual Studio break on any exception, not just the unhandled ones. Use Ctrl-Alt-E to edit – there is supposed to be some way to get to it though the menu, but I’ve not found it. Discovered in a blog post here.