我应该如何使用 Fluent API 配置这些模型之间的关系？答案

【问题标题】：How should I configure relationships between these models with Fluent API?我应该如何使用 Fluent API 配置这些模型之间的关系？
【发布时间】：2020-11-06 08:42:00
【问题描述】：

我收到此错误“在表 'Tasks' 上引入 FOREIGN KEY 约束 'FK_Tasks_Projects_ProjectId' 可能会导致循环或多个级联路径”

Project 类中的任务可以为空，用户也可以没有 TeamId。


public class Task {
    public int Id {get; set;}
    public int ProjectId {get; set;}
    public int PerformerId {get; set;}
    public User Performer {get; set;}
}

public class Project {
    public int Id {get; set;}
    public int AuthorId {get; set;}
    public int TeamId {get; set;}
    public List<Task> Tasks {get; set;}
    public User Author {get; set;}
    public Team Team {get; set;}
}

public class Team {
    public int Id {get; set;}
}

public class User {
    public int Id {get; set;}
    public int ?TeamId {get; set;}
}

【问题讨论】：

标签： c# database entity-framework-core asp.net-core-webapi fluent

【解决方案1】：

这里有一个类似的帖子：Entity Framework Core: How to solve Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths

为了简化这一点，我只需将用户的 id 捕获为项目和任务的 int（而不是用户实体）。

public class Task {
    public int Id {get; set;}
    public int ProjectId {get; set;}
    public int PerformerId {get; set;}
}

public class Project {
    public int Id {get; set;}
    public int AuthorId {get; set;}
    public int TeamId {get; set;}
    public List<Task> Tasks {get; set;}
    public int Author {get; set;}
    public Team Team {get; set;}
}

public class Team {
    public int Id {get; set;}
}

public class User {
    public int Id {get; set;}
    public int ?TeamId {get; set;}
}

最终我会选择像这样稍微不同的结构：

public class Task
{
    public int TaskID { get; set; }
    public int ProjectID { get; set; }
    public int PerformerID { get; set; }
}

public class Project
{
    public int ProjectID { get; set; }
    public int AuthorID { get; set; }
    public int TeamID { get; set; }
    public List<Task> Tasks { get; set; }
    public Team Team { get; set; }
}

public class Team
{
    public int TeamID { get; set; }
}

public class User
{
    public int UserID { get; set; }
    public List<Team> Teams { get; set; }
}

【讨论】：