Entity Framework Core Delete Behavior

Question

So I have these 3 tables where 2 of them(Post(Parent of Comment table as well) and Comment Table) is parent of Reaction Table.

Post Table:

public class Post
{
    public long Id { get; set; }
    [MaxLength(800)]
    public string Message { get; set; }
    public string FilePath { get; set; }
    [Required]
    public short Audience { get; set; }
    [Required]
    public bool AreCommentsAllowed { get; set; }
    public DateTime DatePosted { get; set; }
    public ICollection<Comment> Comments { get; set; }
    public ICollection<Reaction> Reactions { get; set; }
    public int? GroupId { get; set; }
    public Group Group { get; set; }
    [Required]
    public string UserId { get; set; }
    public User User { get; set; }
}

Comment Table:

 public class Comment
{
    public long Id { get; set; }
    [MaxLength(800)]
    public string Message { get; set; }
    public string FilePath { get; set; }
    [Required]
    public DateTime DateCommented { get; set; }
    public ICollection<Reaction> Reactions { get; set; }
    public long? PostId { get; set; }
    public Post Post { get; set; }
    public long? ReplyId { get; set; } // For replies on this comment
    [Required]
    public string UserId { get; set; }
    public User User { get; set; }
}

Reaction Table:

public class Reaction
{
    public long Id { get; set; }
    [Required]
    public short ReactionTypeId { get; set; }
    public ReactionType ReactionType { get; set; }
    public DateTime DateReacted { get; set; }
    public long? PostId { get; set; }
    public Post Post { get; set; }
    public long? CommentId { get; set; }
    public Comment Comment { get; set; }
    [Required]
    public string UserId { get; set; }

    public User User { get; set; }
}

What I want to happen is when I delete the post these records reactions, comments and comment reactions will be deleted as well. To achieve this behavior I used these configuration on fluent API.

builder.Entity<Post>()
            .HasMany(x => x.Comments)
            .WithOne(x => x.Post)
            .OnDelete(DeleteBehavior.Cascade);


        builder.Entity<Post>()
            .HasMany(x => x.Reactions)
            .WithOne(x => x.Post)
            .OnDelete(DeleteBehavior.Cascade);

        builder.Entity<Comment>()
            .HasMany(x => x.Reactions)
            .WithOne(x => x.Comment)
            .OnDelete(DeleteBehavior.Cascade);

However, after running the update-database it shows the error : Introducing FOREIGN KEY constraint 'FK_Reactions_Posts_PostId' on table 'Reactions' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

Answer 1

This is because when you delete a Post you have two paths where you would delete a Reaction (in the relationship with Posts and with the Relationship with Comments which will also be deleted). Just set one of the Relationships DeleteBehavior to NoAction to fix this.