[SalesForce] Visualforce Page as the Default Layout of an Object (Standard/Custom)

As an alternative to using standard page layouts, you can use FieldSets. You can create several field sets and have your controller fetch the correct one with similar criteria as the page layouts. You can then use the field set to dynamically render your page. Basically, you will use an <apex:repeat> paired with <apex:pageBlockSecions> in order to simulate a Page Layout. (Not quite the same thing, but the closest I've found so far.)

yes it is.

go to Case --> buttons, link, Actions then find the Label "edit" and select the action edit. .. then you can override the std page with that vf one.

Now, say if you want to choose between a std page and the vf page? What you'd do is create a routing VF page. So, when the user clicks edit, he goes to the router. based on what ever criteria (i.e. ecternal user / internal user), he'll get sent to where he needs to go.

Example

if you need any paramaters from your previous page, you can get those via a referring page. you can make this call in your constructor to build your retURL for a cancel action, or if you need the referrinf record in any way

 //vf page
apex:page action={!router}>

 // in  controller

public pagerefernce getRouter()
    PageReference p ;   
    if ($UserInfo.getProfileId == '') <-- external profile{
        p = new PageReference(/apex/YourVFPage);
        }else{
        p = new PageReference('/'+this.case.id+ '/e?nooveride=1'
        }
    return p;
}