How to configure cascade deletion in Entity Framework Core 8

Question

I'm new to .NET and Entity Framework Core (v8), and I'm wondering if there's a way to configure cascade deletion for the following

scenario:

When I delete a File entity (database row), I want all associated entities to be deleted as well. Currently, I'm encountering a foreign key error when I attempt to delete a File entity.

public class File
{
    public Guid Id { get; set; }
    public string? Name { get; set; }
    public string? Type { get; set; }
    public DateTime UploadedDate { get; set; }
    public string UploadedBy { get; set; }
    public string? FileUrl { get; set; }
    public FileType FileType { get; set; }
}

public class Entity1
{
   public Guid Id { get; set; }
   public Guid? FileId { get; set; }
   public File? File { get; set; }
}

public class Entity2
{
   public Guid Id { get; set; }
   public Guid? FileId { get; set; }
   public File? File { get; set; }
}

public class Entity3
{
    public Guid Id { get; set; }
    public Guid? FileId { get; set; }
    public File? File { get; set; }
}

public async Task Delete(Guid fileId)
{
     var file = await _dbContext.FileMetadatas
                      .FirstOrDefaultAsync(sr => sr.Id == fileId);

     var fileInfo = new FileInfo(file.FileUrl);
     _dbContext.FileMetadatas.Remove(file);

     await _dbContext.SaveChangesAsync();
     if (fileInfo.Exists)
     {
           fileInfo.Delete();
     }
}

Answer 1

Add this in your dbContext file:

OnDelete(DeleteBehavior.Cascade)

As shown bellow

public class MyDbContext : DbContext
    {
        public DbSet<File> Files { get; set; }
        public DbSet<Entity1> Entity1s { get; set; }
        public DbSet<Entity2> Entity2s { get; set; }
        public DbSet<Entity3> Entity3s { get; set; }
    
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<File>()
                .HasMany(f => f.Entity1s)
                .WithOne(e => e.File)
                .HasForeignKey(e => e.FileId)
                .OnDelete(DeleteBehavior.Cascade);
    
            modelBuilder.Entity<File>()
                .HasMany(f => f.Entity2s)
                .WithOne(e => e.File)
                .HasForeignKey(e => e.FileId)
                .OnDelete(DeleteBehavior.Cascade);
    
            modelBuilder.Entity<File>()
                .HasMany(f => f.Entity3s)
                .WithOne(e => e.File)
                .HasForeignKey(e => e.FileId)
                .OnDelete(DeleteBehavior.Cascade);
        }
    }

After configuring the relationships, you can delete a File and all related entities will be deleted as well.