如何进行Task.CompletedTask和Task.Result分析

public interface IComputer    {        Task Do();    Task DoString();}

public class Computer : IComputer    {        public Task Do()        {          return Task.Run(() => {            //逻辑代码         });    }    public Task DoString()            {                return Task.Run( () => {        //逻辑代码 return "aaa";        });     }}

public Task Do()        {                    //逻辑代码        return Task.CompletedTask;    }

/// 
Gets a task that has already completed successfully.
/// The successfully completed task.public static Task CompletedTask { get; }

public Task DoString() {    //逻辑代码    return Task.FromResult("aaa");}

/// 
Creates a  that's completed successfully with the specified result.
/// The result to store into the completed task./// The type of the result returned by the task./// The successfully completed task.public static Task FromResult<[Nullable(2)] TResult>(TResult result);