In order to create a breadcrumb, you will need to be aware of the GetAncestors method. Get Ancestor will return a list of pages from the users current page in the page tree, back to the start page. A few code examples using GetAncestors:
Moving back to the breadcrumb, we will also need to use the CompareToIgnoreWorkID(ContentReference) method so while we iterate back up, the page tree we know when we have hit the start page. CompareToIgnoreWorkID compares a ContentReference to another instance. One word of warning about CompareToIgnoreWorkID, is that it only compares against a content ID and the ProviderName for equality (there is also a similar Epi API call, called Equals that compares against content ID, ProviderName and WorkID.
Working Code Example
All the above code can be downloaded in a fully working website from my github account here. #ILoveEpiserver