How to check Foreign Key to restrict SoftDelete?

Question

I would like to know if it is possible to check FK when using SoftDelete with ASP.NET Boilerplate.

Example

Suppose these tables:

Roles: RoleId (PK) - Description
Users: UserId (PK) - Name - RoleId (FK with Roles)

Data:

Roles
1 - admin
2 - guest

Users
1 - admin - 1
2 - john - 2

So RoleId 1 should not be deleted if it was already assigned to an existing User.

Thanks in advance.

Answer 1

Soft delete just sets a flag to mark the record as deleted.

In ABP, you can write your own checks in ApplyAbpConceptsForDeletedEntity of your DbContext:

public class AbpProjectNameDbContext // : ...
{
    // ...

    protected override void ApplyAbpConceptsForDeletedEntity(EntityEntry entry, long? userId, EntityChangeReport changeReport)
    {
        CheckForeignKeys(entry);

        base.ApplyAbpConceptsForDeletedEntity(entry, userId, changeReport);
    }

    private void CheckForeignKeys(EntityEntry entry)
    {
        var entity = entry.Entity;
        if (!(entity is ISoftDelete))
        {
            // Foreign key constraints checked by database
            return;
        }

        var role = entity as Role;
        if (role != null)
        {
            if (Users.Any(u => u.Roles.Any(r => r.RoleId == role.Id)))
            {
                throw new UserFriendlyException("Cannot delete assigned role!");
            }
        }
    }
}

Note that the template's RoleAppService actually removes users from the role before deleting it.