ASP.NET MVC 3 (final) was released today. When this version was in its infancy I remember reading on codeplex that donut caching was being considered. Does anyone know if this made it into V3? I cannot seem to find any information so I can only (sadly) assume that it didn't happen.
Yes, it is. Scott Gu blogged about it:
In addition to supporting full page output caching, ASP.NET MVC 3 also supports partial-page caching – which allows you to cache a region of output and re-use it across multiple requests or controllers. The [OutputCache] behavior for partial-page caching was updated with RC2 so that sub-content cached entries are varied based on input parameters as opposed to the URL structure of the top-level request – which makes caching scenarios both easier and more powerful than the behavior in the previous RC.
UPDATE:
Out of the box only donut hole caching is supported in ASP.NET MVC 3. This allows you to cache a small portion of the page by using the [OutputCache] attribute on a child action. Donut caching which allows for excluding portions of a page that has been cached is not supported. Response.WriteSubstitution doesn't work since ASP.NET MVC 2. Here is a good article which explains the different caching options available in ASP.NET MVC 3.
UPDATE 2:
Here's a great article which illustrates how donut caching could be enabled in ASP.NET MVC 3.