SQLite.Net SQLiteException Constraint

Question

I've looked here before with this error but the results won't work for me.

I have made a login form and it works fine for one time. After I logged in once and restart the app and try to log in I'm getting the error.

Function:

public int SaveUser(User user)
{
    lock (locker)
    {
        if (user.Id != 0)
        {
            database.Update(user);
            return user.Id;
        }

        else
        {
            return database.Insert(user);
        }
    }
}

User model:

[Table("User")]
public class User
{   
    [PrimaryKey, AutoIncrement, NotNull]
    public int Id { get; set; }
    [Unique]
    public string Username { get; set; }
    public string Password { get; set; }
}

Update: I hope this are the details that's needed for further help.

02-27 14:13:15.806 I/MonoDroid(23447): at SQLite.PreparedSqlLiteInsertCommand.ExecuteNonQuery (System.Object[] source) [0x00121] in /Users/vagrant/git/src/SQLite.cs:2668 02-27 14:13:15.806 I/MonoDroid(23447): at SQLite.SQLiteConnection.Insert (System.Object obj, System.String extra, System.Type objType) [0x000f4] in /Users/vagrant/git/src/SQLite.cs:1415 02-27 14:13:15.806 I/MonoDroid(23447): at SQLite.SQLiteConnection.Insert (System.Object obj) [0x00005] in /Users/vagrant/git/src/SQLite.cs:1281 02-27 14:13:15.806 I/MonoDroid(23447): at KleynGroup.Data.UserDatabaseController.SaveUser (KleynGroup.User user) [0x00038] in C:\Users\[name]\source\repos\KleynGroup\KleynGroup\KleynGroup\Data\UserDatabaseController.cs:48

Sorry if there are a lot of mistakes. I'm new to Xamarin and still learning.

I hope you guys can help me

There is more detail to the error than that, please show it, but I'm sure it is because you are trying to insert a user that already exits. — Crowcoder
– Crowcoder, Commented Feb 27, 2018 at 13:04
Have you verified, that the !=null branch is taken? What exception is thrown? With that little details it's hard to tell what is going wrong. — Paul Kertscher
– Paul Kertscher, Commented Feb 27, 2018 at 13:08
I edited the question with the right details i hope (more isn't givne) — Swiffer
– Swiffer, Commented Feb 27, 2018 at 13:20

Paul Kertscher · Accepted Answer · 2018-02-27 13:23:22Z

2

According to the error messages the exception is thrown by Insert, hence I'd assume that you are trying to insert the User (User.Id seems to be 0). Anyway, since it's not a new, but an existing user name, inserting it fails because of the UNIQUE constraint of Username.

You have to make sure, that when the user is loaded and then saved, it still has the correct ID, to prevent that exception.

answered Feb 27, 2018 at 13:23

Paul Kertscher

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