Returning a string from LINQ - string

Question

For a school project we have to create an evaluation website that requires a login.
For the database connection I chose LINQ, because it's new and is supposed to be easier/better in use.
I managed to create a login check with the following:
public static Boolean Controle(int id, string wachtwoord)
{
DataClassesDataContext context = new DataClassesDataContext();
var loginGebruiker =
from p in dc.Gebruikers
where p.GebruikerID == id
where p.GebruikerWachtwoord == wachtwoord
select p;
return true;
}
Now I'm trying to create a "forgot password" option, where you enter your id and the password gets returned (later it would be emailed to you, don't know how I would do this either, suggestions?)
I tried with the following code:
public static string Forgot(int id)
{
var context = new DataClassesDataContext();
var wachtwoordLogin = (
from p in dc.Gebruikers
where p.GebruikerID == id
select p.GebruikerWachtwoord);
return wachtwoordLogin.ToString();
}
Code behind the button on the page:
lbl1.Text = Class1.Forgot(Convert.ToInt32(txt1.Text));
Now when I enter the an id of the first user (1), lbl1 becomes this:
SELECT [t0].[GebruikerWachtwoord] FROM
[dbo].[Gebruiker] AS [t0] WHERE
[t0].[GebruikerID] = #p0
I don't know how to solve this and I have been looking everywhere, I hope somebody can help me.
Thanks,
Thomas

Answer 1

LINQ uses delayed execution, so your 'wachtwoordLogin' is really just "how to get your data." Its not until you apply an operator that LINQ will actually attempt to retrieve your data.
Your first statement:
var loginGebruiker = (
from p in dc.Gebruikers
where p.GebruikerID == id
where p.GebruikerWachtwoord == wachtwoord
select p).FirstOrDefault()
if (loginGeruiker != null) {
//Valid login
} else {
// invalid
}
FirstOrDefault means, take the first item in the list, or return none.
In you other case you need the same thing:
user = wachtwoordLogin.FirstOrDefault();
Further reading: MSDN 101 LINQ Samples
For your question about emailing a forgotten password, have you ever thought about implementing the golden questions algorithm instead? Its simplified, and does the same thing.
Basically, at the time of registering just get them to answer some questions, and if they can verify them, allow them to reset the password.

Answer 2

you enter your id and the password gets returned
What, then, is the point of having a password if anybody who knows a username can see it? I know this isn't what you're asking, but for someone getting started in programming I feel a duty to point this out. What you're creating here is essentially a completely broken login model. Nobody should ever use a system like this.
You should never ever display a password. Not on the screen, not in an email, never.
Passwords, if they even need to be stored at all (CodingHorror has had a couple of good posts on this lately, advocating things like OpenID), should be stored in hashed form and essentially unable to be retrieved. When a user logs in, similarly hash the password they provide (immediately upon reaching the application code, before transporting it anywhere else in the system) and compare that to the stored hashed version.
If the user asks for his password, you don't have it. You can't give it to him. This is for his protection. Instead of providing the user with his password, if it's forgotten then you provide the user with a means to reset his password (sending an email to the address on file with a temporarily available URL, a set of "security questions" to verify his identity, etc.) so that he can enter a new one to overwrite the old one. But you shouldn't be able to "show" the user his password because even you as the administrator of the system shouldn't be able to see it in any usable form.

Answer 3

wachwoordLogin will be an IQueryable so you can get this by using FirstOrDefault() which will return null if not found:
(from p in dc.Gebruikers
where p.GebruikerID == id
select p.GebruikerWachtwoord).FirstOrDefault();