Detect invalid VerifyAccess calls

[randymarsh77]

Calling (Dispatcher.)VerifyAccess() (typically through NotifyPropertyChangedDispatcherBase) from a non dispatcher-affined thread (typically, any threadpool thread) causes an application crash. Yet, this is a very common developer mistake that results in wasted time at the very least.

Detecting the dispatcher context of calls to VerifyAccess seems possible, though computationally intensive. Doing a fixed N-level deep search on code in the scope of a switch to the threadpool seems like it might be less computationally expensive, and still provide value.

However, perhaps the biggest challenge would be to resolve variant runtime behavior in order to properly detect invalid code. e.g.

context.Switch(await context.ToThreadPool());
if (x) context.Switch(await context.ToSyncContext());
if (y) VerifyAccess();