Dear Sir/Madam
I have experience working with various commercial trading and technical analysis platforms (MT4, Metastock) and implementing custom trading platforms and indicators/strategies. I downloaded City Index's platform and had a quick look. Implementation of indicators can be done in C#. There is a built-in (horizontal) support/resistance indicator that you can try out to see if it is suitable for use in your project. I haven't found a formula yet for the oblique support and resistance bands, but, since you mentioned MT4, if you have some specific implementation in mind from that (or another) platform, it is possible to copy the functionality. Indicator properties will be adjustable by the user, so, for example, you will be able to choose any period you want for the moving averages. Thank you in advance.
Yours Faithfully
Alex