VSTHRD114.md

VSTHRD114 Avoid returning a null Task

Returning null from a non-async Task/Task<T> method will cause a NullReferenceException at runtime. This problem can be avoided by returning Task.CompletedTask, Task.FromResult<T>(null) or Task.FromResult(default(T)) instead.

Examples of patterns that are flagged by this analyzer

Any non-async Task returning method with an explicit return null; will be flagged.

Task DoAsync() {
    return null;
}

Task<object> GetSomethingAsync() {
    return null;
}

Solution

Return a task like Task.CompletedTask or Task.FromResult.

Task DoAsync() {
    return Task.CompletedTask;
}

Task<object> GetSomethingAsync() {
    return Task.FromResult<object>(null);
}