Comparing Database values with an input value?

Question

I'm attempting to create a register page for users to use. However, this allows users to have the same Username, in which I don't want to happen. I've wrote a piece of code, which I assumed would work but failed miserably.

Managers manager = new Managers();

//Compares to database to find any duplicate usernames
if (manager.Username == txtUsername.Text)
{
    lblUsername.Text = "Please enter a different username!";
    lblUsername.Visible = true;
}

Only gave the relevant part.

I was wondering if someone could explain to me what I have done wrong about this? Managers is my database.

Edit- I added in a foreach loop, however was still accepted values.

List<Managers> manage = new List<Managers>();
Managers manager = new Managers();
foreach (Managers m in manage)
{
    if (manager.Username == txtUsername.Text)
    {
        lblUsername.Text = "Please enter a different username!";
        lblUsername.Visible = true;
    }
}

https://i.sstatic.net/pxpGI.png Showing the Error when program is ran

Although, it looks as though you're missing a loop, as you're only going to be checking the first "Managers" record with that code. Possibly something like: foreach(Managers m in manager) { // do your check here } — NoGall
– NoGall, Commented Dec 19, 2014 at 13:09
It simply does not search the managers database for any login with the same username. I will attempt a loop just now. — Brian Elliott
– Brian Elliott, Commented Dec 19, 2014 at 13:11
You say "Managers is my database". Are you sure? On the face of it, it looks like a simple class that represents a manager. — Coding Flow
– Coding Flow, Commented Dec 19, 2014 at 13:19
My database is called 'ManagersDbContext'. I just realised my flaw. Thank you for the help. — Brian Elliott
– Brian Elliott, Commented Dec 19, 2014 at 13:24

xwpedram · Accepted Answer · 2014-12-20 13:22:23Z

2

Do something like :

var query = (from c in db.Users where c.UserName== userName select c);
if (query.Count() > 0)
{
    // Message : user is exist 
}
else
{
   // register user
}

Edit :

Use lambda expressions

if (Manager.Users.Select(d => d).Where(d => d.UserName == UserName).ToList().Count() > 0)
{
        // the Item is Exist in the list
}
else
{
        Manager.Users.Add(new Users { UserName = Username, Pass= Password});
}

edited Dec 20, 2014 at 13:22

answered Dec 19, 2014 at 13:28

xwpedram

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