public class Task : Entity<long>
{
  [ForeignKey("AssignedPersonId")]
  public virtual Person AssignedPerson { get; set; }

  public virtual int? AssignedPersonId { get; set; }

  public virtual string Description { get; set; }

  public virtual DateTime CreationTime { get; set; }

  public virtual TaskState State { get; set; }

  public Task()
  {
    CreationTime = DateTime.Now;
    State = TaskState.Active;
  }
}

public class Person : Entity
{
  public virtual string Name { get; set; }
}

DbMigrationsConfiguration<SimpleTaskSystem.EntityFramework.SimpleTaskSystemDbContext>
{
  public Configuration()
  {
    AutomaticMigrationsEnabled = false;
  }

  protected override void Seed(SimpleTaskSystem.EntityFramework.SimpleTaskSystemDbContext context)
  {
    context.People.AddOrUpdate(
      p => p.Name,
      new Person {Name = "Isaac Asimov"},
      new Person {Name = "Thomas More"},
      new Person {Name = "George Orwell"},
      new Person {Name = "Douglas Adams"}
      );
  }
}

public partial class InitialCreate : DbMigration
{
  public override void Up()
  {
    CreateTable(
      "dbo.StsPeople",
      c => new
        {
          Id = c.Int(nullable: false, identity: true),
          Name = c.String(),
        })
      .PrimaryKey(t => t.Id);
      
    CreateTable(
      "dbo.StsTasks",
      c => new
        {
          Id = c.Long(nullable: false, identity: true),
          AssignedPersonId = c.Int(),
          Description = c.String(),
          CreationTime = c.DateTime(nullable: false),
          State = c.Byte(nullable: false),
        })
      .PrimaryKey(t => t.Id)
      .ForeignKey("dbo.StsPeople", t => t.AssignedPersonId)
      .Index(t => t.AssignedPersonId);      
  }
    
  public override void Down()
  {
    DropForeignKey("dbo.StsTasks", "AssignedPersonId", "dbo.StsPeople");
    DropIndex("dbo.StsTasks", new[] { "AssignedPersonId" });
    DropTable("dbo.StsTasks");
    DropTable("dbo.StsPeople");
  }
}

PM> Update-Database

public interface ITaskRepository : IRepository<Task, long>
{
  List<Task> GetAllWithPeople(int? assignedPersonId, TaskState? state);
}

public class TaskRepository : SimpleTaskSystemRepositoryBase<Task, long>, ITaskRepository
{
  public List<Task> GetAllWithPeople(int? assignedPersonId, TaskState? state)
  {
    //在仓储方法中，不用处理数据库连接、DbContext和数据事务，ABP框架会自动处理。
      
    var query = GetAll(); //GetAll() 返回一个 IQueryable<T>接口类型
      
    //添加一些Where条件

    if (assignedPersonId.HasValue)
    {
      query = query.Where(task => task.AssignedPerson.Id == assignedPersonId.Value);
    }

    if (state.HasValue)
    {
      query = query.Where(task => task.State == state);
    }

    return query
      .OrderByDescending(task => task.CreationTime)
      .Include(task => task.AssignedPerson)
      .ToList();
  }
}

public interface ITaskAppService : IApplicationService
{
  GetTasksOutput GetTasks(GetTasksInput input);
  void UpdateTask(UpdateTaskInput input);
  void CreateTask(CreateTaskInput input);
}

public class TaskAppService : ApplicationService, ITaskAppService
{
  private readonly ITaskRepository _taskRepository;
  private readonly IRepository<Person> _personRepository;
    
  /// <summary>
  /// 构造函数自动注入我们所需要的类或接口
  /// </summary>
  public TaskAppService(ITaskRepository taskRepository, IRepository<Person> personRepository)
  {
    _taskRepository = taskRepository;
    _personRepository = personRepository;
  }
    
  public GetTasksOutput GetTasks(GetTasksInput input)
  {
    //调用Task仓储的特定方法GetAllWithPeople
    var tasks = _taskRepository.GetAllWithPeople(input.AssignedPersonId, input.State);

    //用AutoMapper自动将List<Task>转换成List<TaskDto>
    return new GetTasksOutput
        {
          Tasks = Mapper.Map<List<TaskDto>>(tasks)
        };
  }
    
  public void UpdateTask(UpdateTaskInput input)
  {
    //可以直接Logger,它在ApplicationService基类中定义的
    Logger.Info("Updating a task for input: " + input);

    //通过仓储基类的通用方法Get，获取指定Id的Task实体对象
    var task = _taskRepository.Get(input.TaskId);

    //修改task实体的属性值
    if (input.State.HasValue)
    {
      task.State = input.State.Value;
    }

    if (input.AssignedPersonId.HasValue)
    {
      task.AssignedPerson = _personRepository.Load(input.AssignedPersonId.Value);
    }

    //我们都不需要调用Update方法
    //因为应用服务层的方法默认开启了工作单元模式（Unit of Work）
    //ABP框架会工作单元完成时自动保存对实体的所有更改，除非有异常抛出。有异常时会自动回滚，因为工作单元默认开启数据库事务。
  }

  public void CreateTask(CreateTaskInput input)
  {
    Logger.Info("Creating a task for input: " + input);

    //通过输入参数，创建一个新的Task实体
    var task = new Task { Description = input.Description };

    if (input.AssignedPersonId.HasValue)
    {
      task.AssignedPersonId = input.AssignedPersonId.Value;
    }

    //调用仓储基类的Insert方法把实体保存到数据库中
    _taskRepository.Insert(task);
  }
}

public class CreateTaskInput : IInputDto
{
  public int? AssignedPersonId { get; set; }

  [Required]
  public string Description { get; set; }
}

public class UpdateTaskInput : IInputDto, ICustomValidate
{
  [Range(1, long.MaxValue)]
  public long TaskId { get; set; }

  public int? AssignedPersonId { get; set; }

  public TaskState? State { get; set; }

  public void AddValidationErrors(List<ValidationResult> results)
  {
    if (AssignedPersonId == null && State == null)
    {
      results.Add(new ValidationResult("AssignedPersonId和State不能同时为空!", new[] { "AssignedPersonId", "State" }));
    }
  }
}

DynamicApiControllerBuilder
  .ForAll<IApplicationService>(Assembly.GetAssembly(typeof (SimpleTaskSystemApplicationModule)), "tasksystem")
  .Build();