Asynchronous methods

Supported return types

A method is asynchronous (IsMethodAsync is true) when its return type follows the awaitable pattern: it has a GetAwaiter() method that returns an awaiter with IsCompleted, GetResult() and OnCompleted. This covers:

• Task and Task<T>, ValueTask and ValueTask<T>;
• custom awaitable types, including those whose awaiter only implements INotifyCompletion;
• F# Async<T> (FSharpAsync<T>), which is started as a task. The executor finds the F# types at run time, so applications that do not use F# do not need FSharp.Core.

ExecuteAsync returns an ObjectMethodExecutorAwaitable. Awaiting it gives the result of the method as an object, or null when the awaitable has no result, such as a Task or an F# Async<unit>.

Avoid the boxing of ExecuteAsync

ExecuteAsync works for every awaitable type, but it has to handle the awaitable, its awaiter and the result as object values, which can allocate. When you know the return type of the method, call Execute and await the result you get:

var executor = ObjectMethodExecutor.Create(typeof(Sample).GetMethod(nameof(Sample.AsyncMethod))!);

// Execute returns the Task<int> returned by the method
var task = (Task<int>)executor.Execute(new Sample { Offset = 10 }, [1, 2])!;
Assert.Equal(13, await task);

async void methods

An async void method returns nothing to await, so IsMethodAsync is false. Execute starts it and returns null without waiting for it to complete. ExecuteAsync throws an InvalidOperationException for such a method: use Execute.

Value types

For an instance method of a struct, pass the boxed value as the target. A method that changes the struct changes the boxed instance, as MethodInfo.Invoke does.