ASP.NET MVC - Can't access a parent class in a database relationship (LINQ TO SQL)

I have a class User and a 开发者_Python百科class History. History has 'User' property, and User has 'Histories' property. So there's a database relationship.

But when I create a new User history class and set UserID property, I can't access the 'User' property.

var history = new History { UserID = 1 };
// history.User = null ???

How can I get the user?

I think you need to create a new User and then set the UserID property:

var history = new History();

history.User = new User { UserID = 1 };