Understanding Sandboxed Solutions
There are several components/processes that are involved in the execution of sandboxed solutions. For a developer, it's critical to understand how coding/debugging various types of solutions changes based on the type of solution. Here's how the execution goes in a nutshell: When the sandboxed code is called, the Execution Manager (running in the w3wp.exe) makes a call to an application server running the User Code Service (SPUCHostService.exe). The User Code Service then tells the Worker Service (SPUCWorkerProcess.exe) to load the sandbox code. The code is then verified to ensure only calls to the subset of the API allowed by the Sandbox API are called. The worker process then executes the code against the Worker Proxy (SPUCWorkerProcessProxy.exe) which has full access to the SharePoint API (but the sandboxed code has already been disallowed from using the non-subset portion of the API by the Worker Service). When debugging sandboxed solution...