legacy application function how to update

// Quotes..
e.RenderedHtml = Transforms.BBQuoteCodeToHtml(e.RenderedHtml);

// Emoticons..
e.RenderedHtml = Transforms.EmoticonTransforms(e.RenderedHtml);

// Other BB..
e.RenderedHtml = Transforms.BBcodeToHtml(e.RenderedHtml);

In an application how do we achieve this going forwards?