Add new data with Entity Framework

Question

I am trying to add new data to my database, here is my code:

// This is the dbContext
private BugTrackerDBContainer db = new BugTrackerDBContainer();

//The objet with its properties
public static Developper devAdded = new Developper();
devAdded.Name = txb_name.Text;
devAdded.FirstName = txb_firtname.Text;

// Add to the database
db.AddToDevelopper(devAdded);
db.SaveChanges();

My problem is that it I launch it once, it works fine, but twice I am having this error:

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

Why is it ?

Thanks for your helps

Answer 1

What are all this mix of function and variables declaration?
You are trying to add the same static instance object twice to the same DataContext, it will fail.

• Don't declare static variables. Is is bad.
• Don't declare you Context as a field. Use it as a local variable with using blocks.
• Don't mix access to UI element like textboxes with manipulation of database. Create layer in your application.

An example :

public void AddDevelopperButton_Click(object sender, EventArgs e)
{
    this.AddDevelopper(txb_name.Text, txb_firtname.Text);
}

public Developper AddDevelopper(string name, string firstName)
{
    Developper devAdded = new Developper();
    devAdded.Name = name;
    devAdded.FirstName = firstName;

    using(BugTrackerDBContainer db = new BugTrackerDBContainer())
    {
        db.AddToDevelopper(devAdded);
        db.SaveChanges();
    }
    return devAdded;
}

Answer 2

You shouldn't have your database entity as a static object. The problem is most likely this line:

public static Developper devAdded = new Developper();

Change the code to what was recommended by @Scorpi0.

Answer 3

My suggestions are:

A: Learn basic programming

What possible reason declare static:

public static Developper devAdded = new Developper();

B: Then start looking into EF and other frameworks later.