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POQuestion about Repositories and their Save methods for domain objects
 

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  1. POQuestion about Repositories and their Save methods for domain objects
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    <p>I have a somewhat ridiculous question regarding DDD, Repository Patterns and ORM. In this example, I have 3 classes: <strong>Address</strong>, <strong>Company</strong> and <strong>Person</strong>. A Person is a member of a Company and has an Address. A Company also has an Address. </p> <p>These classes reflect a database model. I removed any dependencies of my Models, so they are not tied to a particular ORM library such as NHibernate or LinqToSql. These dependencies are dealt with inside the Repositories.</p> <p>Inside one of <strong>Repositories</strong> there is a <strong>SavePerson(Person person)</strong> method which <strong>inserts/updates</strong> a Person depending on whether it already exists in the database.</p> <p>Since a Person object has a Company, I currently save/update the values of the Company property too when making that SavePerson call. I insert / update all of the Company's data - Name and Address - during this procedure. </p> <p>However, I really have a hard time thinking of a case where a Company's data can change while dealing with a Person - I only want to be able to assign a Company to a Person, or to move a Person to another Company. I don't think I ever want to create a new Company alongside a new Person. So the SaveCompany calls introduce unnecessary database calls. When saving a Person I should just be able to update the CompanyId column.</p> <p>But since the Person class has a Company property, I'm somewhat inclined to update / insert it with it. From a strict/pure point of view, the SavePerson method should save the entire Person.</p> <p>What would the preferred way be? Just inserting/updating the CompanyId of the Company property when saving a Person or saving all of its data? Or would you create two distinct methods for both scenarios (What would you name them?)</p> <p>Also, another question, I currently have distinct methods for saving a Person, an Address and a Company, so when I save a Company, I also call SaveAddress. Let's assume I use LinqToSql - this means that I don't insert/update the Company and the Address in the same Linq query. I guess there are 2 Select Calls (checking whether a company exists, checking whether an address exists). And then two Insert/Update calls for both. Even more if more compound model classes are introduced. Is there a way for LinqToSql to optimize these calls?</p> <pre><code>public class Address { public int AddressId { get; set; } public string AddressLine1 { get; set; } public string AddressLine2 { get; set; } public string City { get; set; } public string PostalCode { get; set; } } public class Company { public int CompanyId { get; set; } public string Name { get; set; } public Address Address { get; set; } } public class Person { public int PersonId { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public string Email { get; set; } public Company Company { get; set; } public Address Address { get; set; } } </code></pre> <p><strong>Edit</strong></p> <p>Also see <a href="https://stackoverflow.com/questions/679005/how-are-value-objects-stored-in-the-database">this follow up question</a>. How are Value Objects stored in a Database?</p>
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    1. CONo answer because I'm like you on this, but have you considered that if Person is your Aggregate, Company is an immutable value object in this case? Then your Repository wouldn't be concerned with saving properties of Company, just the association itself.
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    2. COIn addition, before mining Generic Repositories, you might read this article by Greg Young. http://codebetter.com/blogs/gregyoung/archive/2009/01/16/ddd-the-generic-repository.aspx
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