EF Core Cascade Delete Discover How to Auto Delete Child Entities

Introduction

Cascade delete allows the deletion of a row to trigger the deletion of related rows automatically.

• EF Core covers a closely related concept and implements several different delete behaviors and allows for the configuration of the delete behaviors of individual relationships.
• In Entity Framework Core, the OnDelete Fluent API method is used to specify the delete behavior for a dependent entity when the principal is deleted.

The OnDelete method takes a DeleteBehavior enum as a parameter:

• Cascade: Child/dependent entity should be deleted
• Restrict: Dependents are unaffected
• SetNull: The foreign key values in dependent rows should update to NULL

Setting a foreign key value to null is not valid if the foreign key is not nullable. The following example set a foreign key field to null when the principal is deleted.

using (var context = new MyContext())
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Invoice>()
            .HasOne(i => i.Customer)
            .WithMany(c => c.Invoices)
            .OnDelete(DeleteBehavior.SetNull+-*);
    }
}

The following example configures the relationship as required and specify that dependant rows are deleted when the principal is deleted.

using (var context = new MyContext())
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Invoice>()
            .HasOne(i => i.Customer)
            .WithMany(c => c.Invoices)
            .IsRequired()
            .OnDelete(DeleteBehavior.Cascade);
    }
}

Delete Behaviors

There are four delete behaviors.

Optional Relationships (nullable foreign key)

It is possible to save a null foreign key value, which results in the following effects.

Required Relationships (non-nullable foreign key)

It is not possible to save a null foreign key value, which results in the following effects: