GraphQL教程（一）。.net Core API2.1

1.创建项目
2.对类库操作，在这里建立三个文件夹，其中一个文件夹改名为schema
3.建立IMovieService,IActorService接口与实现类

GraphQL是什么将放到第二章来讲，第一章为GraphQL的准备工程

1.创建项目

之后选择空项目，.net core 2.1

添加类库，取名

2.对类库操作，在这里建立三个文件夹，其中一个文件夹改名为schema

Movie:用于确定movie类与actor类得类型
Schema：
Service:用来写服务的

安装GraphQL包，加入类库中

在Movies文件夹中建立Movie类，Actor类与枚举MovieRating,MovieRating为Movie中其中一个的枚举
Movie

using GraphStudy.Movies.Movies;
using System;

namespace GraphStudy.Movie.Movies
{
    //电影类
    public class Movie
    {
        public int Id { get; set; }//电影编号
        public string Name { get; set; }
        public DateTime ReleaseDate { get; set; }//上映时间
        public string Company { get; set; }
        public int ActorId { get; set; }//演员ID
        public MovieRating MovieRating { get; set; }//电影等级枚举
    }
}

枚举MovieRating

using System;

namespace GraphStudy.Movies.Movies
{
    [Flags]
    public enum MovieRating
    {
        //这是电影的5个等级
        Unrated = 0,
        G = 1,
        PG = 2,
        PG13 = 3,
        R = 4,
        NC17 = 5
    }
}

Actor演员类,写简单点

namespace GraphStudy.Movies.Movies
{
    //演员类
    public class Actor
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

**

3.建立IMovieService,IActorService接口与实现类

**
在Services文件夹添加IMovieService,IActorService接口与MovieService,ActorServices实现类

IMovieService接口

using GraphStudy.Movies.Movies;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace GraphStudy.Movies.Services
{
    public interface IMovieService
    {
        Task<IEnumerable<Movie>> GetAsyncs();//获取所有列
        Task<Movie> GetByIdAsync(int id);//获取某个对应id属性的列
        Task<Movie> CreateAsync(Movie movie);//创建
    }
}

IActorService接口

using GraphStudy.Movies.Movies;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace GraphStudy.Movies.Services
{
    public interface IActorService
    {
        Task<Actor> GetByIdAsync(int id);//获取某个演员信息
        Task<IEnumerable<Actor>> GetAsync();//获取所有演员信息
    }
}

IMovieService接口的实现类MovieService类

using GraphStudy.Movies.Movies;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace GraphStudy.Movies.Services
{
    public class MovieService : IMovieService
    {
        //因为我们需要创建子列表，所以一要用到IList
        private readonly IList<Movie> _movie;

        public MovieService()
        {
            _movie=new List<Movie>
            {
                #region 电影列表
    
                new Movie
                {
                    Id = 1,
                    Name = "肖申克的救赎The Shawshank Redemption",
                    Company = "美国",
                    MovieRating = MovieRating.G,
                    ActorId = 1,
                    ReleaseDate = new DateTime(1994-10-14)
                },
                new Movie
                {
                    Id = 2,
                    Name = "这个杀手不太冷 Léon ",
                    Company = "法国",
                    MovieRating = MovieRating.NC17,
                    ActorId = 2,
                    ReleaseDate = new DateTime(1994-09-14)
                },
                new Movie
                {
                    Id = 3,
                    Name = "三傻大闹好莱坞",
                    Company = "印度",
                    MovieRating = MovieRating.PG,
                    ActorId = 3,
                    ReleaseDate = new DateTime(2011-12-08)
                },
                new Movie
                {
                    Id = 4,
                    Name = "功夫",
                    Company = "美国",
                    MovieRating = MovieRating.G,
                    ActorId = 4,
                    ReleaseDate = new DateTime(2004-12-23)
                }
                #endregion
            };
        }


        public Task<Movie> CreateAsync(Movie movie)
        {
            _movie.Add(movie);
            return Task.FromResult(movie);
        }

        public Task<IEnumerable<Movie>> GetAsyncs()
        {
            return Task.FromResult(_movie.AsEnumerable());
        }

        public Task<Movie> GetByIdAsync(int id)
        {
            //在这里需要做个判断这个id是否存在
            var movie = _movie.SingleOrDefault(x => x.Id == id);
            if (movie == null)
            {
                throw new ArgumentException(String.Format("Movie ID {0} 不正确", id););
            }

            return Task.FromResult(movie);
        }
    }
}

IActorService接口的实现，ActorService类

using GraphStudy.Movies.Movies;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace GraphStudy.Movies.Services
{
    public class ActorService : IActorService
    {
        private readonly IList<Actor> _actor;

        public ActorService()
        {
            _actor=new List<Actor>
            {
                #region 演员列表

                new Actor
                {
                    Id = 1,
                    Name = "肖申克"
                },
                new Actor
                {
                    Id=2,
                    Name = "让·雷诺"
                },
                new Actor
                {
                    Id = 3,
                    Name = "阿米尔·汗,卡琳娜·卡普尔 ",
                },
                new Actor
                {
                    Id=4,
                    Name = "周星驰,元秋 元华"
                }
                #endregion
            };
        }

        public Task<IEnumerable<Actor>> GetAsync()
        {
            return Task.FromResult(_actor.AsEnumerable());
        }

        public Task<Actor> GetByIdAsync(int id)
        {
            var actor = _actor.SingleOrDefault(x => x.Id == id);
            if (actor == null)
            {
                throw new ArgumentException(String.Format("Actor ID {0} 不存在",id));
            }

            return Task.FromResult(actor);
        }
    }
}

此处注意：Movie与Actor中的ID为一对一，所以ActorService里面new Actor中的id只可唯一，不可以重复，会出错

4.在startup注册服务

添加引用

如果出现以下情况

将类库的版本降为.net core 2.1
右键点击类库->属性

如果无效，请把引用类库取消在引用一次类库
然后进行服务注册

这是第一部分