如何使用实体框架代码优先从数据库中删除所有相关实体答案

【问题标题】：How to delete all related entities from database with Entity Framework code-first如何使用实体框架代码优先从数据库中删除所有相关实体
【发布时间】：2020-06-22 15:55:46
【问题描述】：

我在删除相关实体时遇到问题。例如，我需要从用户系列集合中删除其中一个系列。发生这种情况时，我希望删除数据库中与该系列记录相关的所有内容。怎么做？请提供示例，我有点卡住了。谢谢！

    public class User
    {
        public Guid UserId { get; set; }
        public virtual List<Series> UserSeries { get; set; }
    }

    public class DropPhoto
    {
        public Guid DropPhotoId { get; set; }

        public virtual SimpleLine SimpleHorizontalLine { get; set; }
        public virtual SimpleLine SimpleVerticalLine { get; set; }
        public virtual Drop Drop { get; set; }
    }

    public class ReferencePhoto
    {
        public Guid ReferencePhotoId { get; set; }
        public virtual SimpleLine SimpleLine { get; set; }
    }

    public class Series
    {
        public Guid SeriesId { get; set; }
        public virtual List<DropPhoto> DropPhotosSeries { get; set; }
        public virtual ReferencePhoto ReferencePhotoForSeries { get; set; }          
    }

    public class SimpleLine
    {
        public Guid SimpleLineId { get; set; }
    }

public class Drop
{
    public Guid DropId { get; set; }
}

【问题讨论】：

标签： c# entity-framework code-first

【解决方案1】：

您实际上是在寻找级联删除。

详情请看https://www.entityframeworktutorial.net/code-first/cascade-delete-in-code-first.aspx

这是一个例子

    public class Student
{
    public int StudentId { get; set; }
    public string StudentName { get; set; }

    public virtual StudentAddress Address { get; set; }
}

public class StudentAddress 
{
    [ForeignKey("Student")]
    public int StudentAddressId { get; set; }
    public string Address1 { get; set; }
    public string Address2 { get; set; }
    public string City { get; set; }
    public int Zipcode { get; set; }
    public string State { get; set; }
    public string Country { get; set; }

    public virtual Student Student { get; set; }
}

以下示例演示级联删除操作

using (var ctx = new SchoolContext()) 
{
    var stud = new Student() { StudentName = "James" };
    var add = new StudentAddress() { Address1 = "address" };

    stud.Address = add;

    ctx.Students.Add(stud);

    ctx.SaveChanges();

    ctx.Students.Remove(stud);// student and its address will be removed from db

    ctx.SaveChanges();
}

【讨论】：