Button Click Using Gecko Fx

I have developed a application on c# with default webcontroler but that is eating too much memory and it consumes 500+Mb just in half an hour.So i went for gecko Fx but here come problem.I can't click on the button that doesn't have id.I can see many options like GetElementsByClassName and like that but i can't click on button.
Actually i'm trying to make youtube comment thumb up bot using GeckoFx . Can someone suggest how i can click on the comment thumb up button.
Or It will be also nice to know if there is any method to release that memory from default webcontroler after each request.

Hi

Web browser memory leaks issue cant be solved although there are different solutions mentioned by user but truth is web browser control is having memory leaks issue I tried different solutions like Awesomium,web browser control,httpweb brquest,every one having pro& cons
Gecofx is much better though its little slow but u can automate any thing including AJAX site,Java Script as well
Another thing using web browser control u cant click on java script button

So its better to use Gecofx -
You can click on button by following methods
ID
Name
Inner text/html
Outerhtml
Link
xpath
ByClassName

You please check WEB API REFERENCE OF MOZILLA (I can not post link here)

/en-US/docs/Web/API/element
/en-US/docs/Web/API/Element.outerHTML

if you share the webpage which u r trying automate may be I can provide u some help