LINQ to SQL Stored procedure Insert

Question

Hi I have the following stored procedure:

create procedure dbo.AddNewUser
(
    @uName nvarchar(20),
    @pass nvarchar(20),
    @fName nvarchar(20),
    @lName nvarchar(20)
)
AS
    insert into [Users] (Username, Password, Firstname, Lastname)
    values (@uName, @pass, @fName, @lName)

This is the code for my table:

CREATE TABLE [dbo].[Users] (
    [Id]        INT        IDENTITY (1, 1) NOT NULL,
    [Username]  NCHAR (20) NOT NULL,
    [Password]  NCHAR (20) NOT NULL,
    [Firstname] NCHAR (20) NOT NULL,
    [Lastname]  NCHAR (20) NOT NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

My windows forms program currently has 4 textboxes and 1 button. I am trying to insert the text from the textboxes into my database. This is the code from my click event:

DatabaseConnectionDataContext dc = new DatabaseConnectionDataContext();
dc.AddNewUser(tbUsername.Text, tbPassword.Text, tbFirstname.Text, tbLastname.Text);
dc.SubmitChanges();

When I start the program, enter some data in the textboxes and click the button the data from the textboxes is inserted into the table, but when i start the program again and enter some data into the textboxes, the new data is inserted on the first line instead creating a new line and the old data is erased. Anyone can suggest why is this happening?

Answer 1

You are missing the check if user exists, normally you would do that by id.

using (var dc = new DatabaseConnectionDataContext()){
if (dc.Users.Any(o => o.Username== tbUsername.Text && o.Password == tbPassword.Text ...){
...

}else{dc.AddNewUser(tbUsername.Text, tbPassword.Text, tbFirstname.Text, tbLastname.Text);}

dc.SubmitChanges();
}

EDIT: Having read comment from StefanoGermani
Are you running in memory ravenDb by any chance?