<add name="Default" connectionString="Server=localhost; Database=SimpleTaskSystemDb; Trusted_Connection=True;" />

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; }
}

public class SimpleTaskSystemDbContext : AbpDbContext
{
    public virtual IDbSet<Task> Tasks { get; set; }

    public virtual IDbSet<Person> People { get; set; }

    public SimpleTaskSystemDbContext()
        : base("Default")
    {

    }

    public SimpleTaskSystemDbContext(string nameOrConnectionString)
        : base(nameOrConnectionString)
    {
            
    }
}

internal sealed class Configuration : 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();