How to Implement Cascade Delete for One-to-Zero-or-One Relationships in Entity Framework Code First?

Entity Framework Code First: Cascading Deletes in One-to-Zero-or-One Relationships

In Entity Framework Code First, managing one-to-zero-or-one relationships requires careful consideration of cascading deletes. This ensures that dependent entities are automatically removed when their associated parent entity is deleted.

Let's illustrate with a 'User' and 'UserDetail' scenario. A 'User' may or may not have a 'UserDetail' record. Without proper configuration, deleting a 'User' leaves the related 'UserDetail' record orphaned.

The solution lies in using the fluent API within the OnModelCreating method of your DbContext class:

<code class="language-csharp">protected override void OnModelCreating(DbModelBuilder modelBuilder)
{   
    modelBuilder.Entity<User>()
        .HasOptional(a => a.UserDetail)
        .WithOptionalDependent()
        .WillCascadeOnDelete(true);
}</code>

This code snippet establishes the one-to-zero-or-one relationship using HasOptional and WithOptionalDependent. Crucially, WillCascadeOnDelete(true) activates cascading deletes. Now, deleting a 'User' will automatically remove the corresponding 'UserDetail' entry, maintaining data integrity. This simplifies the Delete method in your UserRepository, ensuring both records are removed in a single operation.

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