Simple way to calculate Response length in MVC4

I was trying to calculate the length of a HTTP Response.
Seems the stream doesn’t want to play. (no read allowed. and the Content-Length doesn’t seem set)
I was hoping to simply call some length property on the HttpContent response.
I have since googled and seen what looks to me like convoluted solutions around filters which I don’t understand.
Is it possible to access the length (content itself is option extra )
If not I would appreciate a link to an example for ‘mvc4/.net 4.5 filter’ included
that I should work though till I do understand. 🙂

How to avoid HttpRequestValidationException in ASP.NET MVC rendering the same view which caused the exception

I just want to know how to validate (or clean) user input in ASP.NET MVC so that an HttpRequestValidationException will not be thrown regardless of the values submitted. For example, with a text input, if the user inputs <BR/>, it will cause an exception and the Yellow Screen of Death will be shown. I don’t want that. I want to catch the exception and to make visible an user friendly error in the current view, preferably with the controls loaded with the same values submitted.

ASP.NET Core Request Localization Options

Here is my custom request culture provider which returns “en” as a default culture if no culture specified in url (for example http://sypalo.com/ru or http://sypalo.com/en).
My idea to show website on that language which is default in user’s browser, so I’m looking a way how to determine it and return it instead of: return Task.FromResult(new ProviderCultureResult(“en”, “en”));