.Net 4 MemoryCache Leaks with Concurrent Garbage Collection

You can “force” a garbage collection right after the problematic method and see if the problem reproduces executing:

System.Threading.Thread.Sleep(200);
GC.Collect();
GC.WaitForPendingFinalizers();

right at the end of the method (make sure that you free any handles to reference objects and null them out). If this prevents memory leakage, and then yes, there may be a runtime bug.