using System;

using System.Reflection;

using System.Threading.Tasks;

​

internal static class TaskExtensions

{

    public static async Task<object> ToGenericTaskAsync(this Task task)

    {

        await task;

        var taskType = task.GetType();

        if (!IsAssignableToGenericTaskType(taskType))

        {

            return null;

        }

​

        return task

            .GetType()

            .GetProperty("Result", BindingFlags.Instance | BindingFlags.Public)!

            .GetValue(task);

    }

​

    private static bool IsAssignableToGenericTaskType(Type type)

    {

        if (type.IsGenericType &&

            type.GetGenericTypeDefinition() == typeof(Task<>) &&

            type.GetGenericArguments()[0] != Type.GetType("System.Threading.Tasks.VoidTaskResult"))

        {

            return true;

        }

​

        return type.BaseType is not null && IsAssignableToGenericTaskType(type.BaseType);

    }

}

​

public static class Program

{

    public static async Task Main()

    {

        Console.WriteLine(await Task.CompletedTask.ToGenericTaskAsync() is null);

        Console.WriteLine(await Task.FromResult<int>(5).ToGenericTaskAsync() is 5);

    }

}

​