VSTHRD001.md

VSTHRD001 Avoid legacy thread switching methods

Switching to the UI thread should be done using JoinableTaskFactory.SwitchToMainThreadAsync rather than legacy methods such as Dispatcher.Invoke or ThreadHelper.Invoke. This avoids deadlocks and can reduce threadpool starvation.

Examples of patterns that are flagged by this analyzer

void Foo() {
    ThreadHelper.Generic.Invoke(delegate {
        DoSomething();
    });
}

Solution

Use await SwitchToMainThreadAsync() instead, wrapping with JoinableTaskFactory.Run if necessary:

void Foo() {
    ThreadHelper.JoinableTaskFactory.Run(async delegate {
        await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
        DoSomething();
    });
}

In the above example, we obtain a JoinableTaskFactory instance from the ThreadHelper.JoinableTaskFactory static property as it exists within Visual Studio itself. Other applications should create and expose their own JoinableTaskContext and/or JoinableTaskFactory for use in code that run in these applications. See our doc on consuming JoinableTaskFactory from a library for more information.

Configuration

This analyzer is configurable via the vs-threading.LegacyThreadSwitchingMembers.txt file. See our configuration topic for more information.