How can I convert html to image?

Take a screenshot.

Or, use the new HTML5 canvas and a library like html2canvas.

How can I convert all the html, beyond the screen. The html2canvas is working like a print screen, if the height is bigger than the screen, it can's see it

Using this example I'm getting the entire page just fine, regardless of screen size.

The only thing I see happening is that dynamically sized elements (like the banner on their example page) get resized to fit the screen when a user resizes the screen, and are thus printed in their smaller size on the resulting image.

Edit: did you select the body element? It seems as if it's printing the contents of the element you select.

There is some way to do this in c#?

You could try following this tutorial if you don't want to do it from the HTML page. It requires a url though.