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

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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.