Using LINQ to SQL to update database?

When I execute the following code I don't get any error, but it doesn't update the changes on the database either. I have 5 entries in the table user, and after executing the following code there is no user with "Active" state in the database.

Am I supposed to write the update statement myself or does it do it for me? What can be the problem here?

var dbContext = new DataClasses1DataContext();

List<user> users = (from u in dbContext.users
                          where u.age < 30
                          select u).ToList();

users[0].state = "Active";
dbContext.SubmitChanges();

EDIT:

So I know what the problem is. I change the State on my object, and the update statement contains the state as a where clause. So when executing the query it can't find an item that matches - it fails on [state] = @p4.

Why is it using all parameters in my update statement when I have a primary key?

UPDATE [dbo].[user]
SET [state] = @p5
WHERE ([id] = @p0) AND ([firstName] = @p1) AND ([lastName] = @p2) 
    AND ([age] = @p3) AND ([state] = @p4)
-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1]
-- @p1: Input NChar (Size = 10; Prec = 0; Scale = 0) [firstName   开发者_开发技巧  ]
-- @p2: Input NChar (Size = 10; Prec = 0; Scale = 0) [lastName  ]
-- @p3: Input Int (Size = -1; Prec = 0; Scale = 0) [25]
-- @p4: Input NChar (Size = 10; Prec = 0; Scale = 0) [Active    ]
-- @p5: Input NChar (Size = 10; Prec = 0; Scale = 0) [Active]

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You need to change the concurrency pattern on your DBML. This website about Updating LINQ-to-SQL entities explains a bit about it.

Anything you don't want to include in the WHERE clause should have their Update Check set to Never on the DBML.

• Open DBML
• Select the state property on your user object
• Press F4 (to see properties)
• Change Update Check (the last setting in the properties) to Never
• Save and try again

Normally I'd turn off Update Check for all columns but you should do more reading to understand exactly how it works in case you need concurrency.

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Apparently, you don't have a primary key on the user table or you didn't specify it in your dbml file. LINQ to SQL only throws exceptions when you insert or delete a record with no primary key. It doesn't throw an exception when updating for some reason.