Linq-To-Sql数据库调用

Question

I couldn't find an answer to this. I'm sure the answer is simple, I don't think I was searching for the right thing.

I have a .dbml file with two tables: Employees and Departments. There's a relationship between the two, Employees has a DepartmentID.

Anyways, I'm doing this in my code:

Employee emp = Employee.Get(123);

string fname = emp.FirstName;
string lname = emp.LastName;
string deptName = emp.Department.Name;
string deptCode = emp.Department.Code;

What I'm wondering is, every time I call emp.Department , is that making a database call? Or was all that information loaded when I created the Employee object?

Answer 1

It made a trip to database, when you first accessed emp.Department.Name unless deferred loading is turned off .

It won't make another trip when you say emp.Department.Code in next statement, it would have already got the Deparment object in memory.

This answer explains it in more detail.

You may want to see

• at what point does linq-to-sql or linq send a request to the database
• Does linq to sql automatically lazy load associated entities?
• Blog: Linq to SQL Deferred Loading - Lazy Load

Answer 2

The query is only executed once to retrieve data. After that it is tracked within the context in memory.

You could verify this using SQL Profiler.