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

Cascade deletion of one-to-zero or one relationship in Entity Framework

In a scenario I encountered recently, a one-to-zero or one relationship was established between two POCO classes User and UserDetail. However, when trying to delete the User record, the foreign key constraints in UserDetail prevent the User record from being deleted due to the lack of cascading deletes.

To solve this problem, Fluent API must be used in DbContext. The following code snippet should be added:

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

A one-to-zero or one relationship between User and UserDetail is established using the HasOptional() and WithOptionalDependent() methods. The WillCascadeOnDelete(true) method then enables cascading deletes for this relationship.

With these changes implemented, deleting a User record will now automatically trigger the deletion of the related UserDetail record.

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