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

possible duplicate of [C# Entity Framework "An entity object cannot be referenced by multiple instances of IEntityChangeTracker"](http://stackoverflow.com/questions/5128361/c-sharp-entity-framework-an-entity-object-cannot-be-referenced-by-multiple-inst) — George Johnston, Apr 24 '13 at 12:42

Cyril Gandon · Accepted Answer · 2013-04-24T12:47:46.263

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;
}

Edit your question and post your entire code. What properties Developper as? Does it have a reference to another property? — Cyril Gandon, Apr 24 '13 at 12:52
I miscopied the code, I tried it once again, works perfectly, cheers for your comments about the best practices, what to do and what not...thanks again — dtjmsy, Apr 24 '13 at 12:54

score 0 · Answer 2 · answered Apr 24 '13 at 12:44

0

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.

answered Apr 24 '13 at 12:44

Garrett Vlieger

8,965
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score 0 · Answer 3 · answered Apr 24 '13 at 15:13

0

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.

answered Apr 24 '13 at 15:13

Mark Homer

609
4
11

Add new data with Entity Framework

3 Answers3