Validate application name

[chrisdunelm]

Validated on setting in Initializer. Fixes #729

[jskeet]

Gosh - I'd never seen that class before. I assume you've checked that it represents the same set of valid values as the servers check?

[chrisdunelm]

This validates that the value is possible/legal to send in the UserAgent header. It's possible the server is more restrictive than this, but this at least ensures the value will get to the server.

[LindaLawton]

Me being curious again:

How do you decide what you want to validate and what you want to just return an error to the user? Isn't it over kill to be checking that its valid every time? Why not just send it and if once out of a thousand it doesn't work then send a nice message to the user that it wont work probably because it cant be sent as a user agent? and tell them it needs to be rfc2616

I realize that checking it probably doesn't take much power but if you check something 1000 times to prevent one fail. Is checking a waste of time?

[jskeet]

@LindaLawton: It's only validated on client initialization, not on every request.

But we've seen it be a tricky issue to diagnose before now, and upfront validation allows us to give a much more specific error.

[LindaLawton]

I have only heard of this issue popping up once or twice in the last five years, so was unaware that it was a bigger issue.

Once again thanks for responding to my curiosity its interesting to hear how other developers approach issues, and how you decide what to address and how.