使用LINQ to SQL时类之间的关系（数据库中没有关系）

Question

I have two tables in my database -> Activities and Customers. Each Activity has a CustomerId, however the designers of the database haven't added any foreign key constraints.

I want to be able to write

activity.Customer.Name //Returns name of the customer 

So I need a way of telling LINQ to SQL to map the CustomerId in the Activity object to the correct Customer object.

I could of course do :

var customers = db.Customers;
var activities = db.Activities;

And then manually map them to each other, but that would be a pain...

Is this is possible? Adding foreign key constraints is unfortunately not an option.

Answer 1

You can write next two lines.

var customer = db.Customers.First(c => c.Id == activity.CustomerId);
var customerName = customer.Name;

One step further write an extension method

static Customer GetCustomer(this Activity)
{
    return db.Customers.First(c => c.Id == activity.CustomerId);
}

and use like

activity.GetCustomer().Name;