Using a GUID as the ID in a database with ASP.NET MVC

Question

I am learning ASP.NET MVC. I am following one of the basic tutorials on asp.net. Since I do not always follow the tutorials to the letter, I decided to use a GUID as the identity column instead of an integer. Everything was working fine until I got up to the point of adding a new record to the database through the MVC application. When I added the new record, it inserted a blank GUID instead of a generated one. Here is the segment of code-behind that handles the insertion:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create([Bind(Exclude = "id")]Movie movieToCreate)
{
    try
    {
        _entities.AddToMovieSet(movieToCreate);
        _entities.SaveChanges();

        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

The [Bind(Exclude = "id")] line 'ignores' the ID column, since it is autogenerated. In the tutorial, the ID is auto-incremented but I think that is because it is an integer. I tried adding a line to this method:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create([Bind(Exclude = "id")]Movie movieToCreate)
{
    try
    {
        movieToCreate.id = Guid.NewGuid();
        _entities.AddToMovieSet(movieToCreate);
        _entities.SaveChanges();

        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

But the id is still an empty GUID. Can anyone provide me with some information on why this is and perhaps how to resolve it?

Apparently removing the [Bind(Exclude)] and keeping the Guid.NewGuid() fixes this issue. I would still like to know why the ID is auto incremented but the GUID is not auto generated. — Anders
– Anders, Commented Aug 19, 2009 at 19:58
Both values are generated on the server. But the EF only sees the int because the SQL Server provider returns generated ints from the server, but not generated IDs. If you disposed the context and re-queried, you'd see both. — Craig Stuntz
– Craig Stuntz, Commented Aug 20, 2009 at 1:57

Community · Accepted Answer · 2017-05-23 12:00:07Z

6

You could use a custom ModelBinder. I learned about those over here.

public class MyClassBinder : DefaultModelBinder {
    protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) {
        var model = (Movie)base.CreateModel(controllerContext, bindingContext, modelType);
        model.id = Guid.NewGuid();
        return model;
    }
}

And your action controller would be:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult MyAction(Movie movieToCreate) {
    // movie should have a new guid in the id
    _entities.AddToMovieSet(movieToCreate);
    _entities.SaveChanges();
}

And you would need to register the binder in Global.asax:

protected void Application_Start() {
    RegisterRoutes(RouteTable.Routes);
    ModelBinders.Binders.Add(typeof(Movie), new MyClassBinder());
}

edited May 23, 2017 at 12:00

CommunityBot

11 silver badge

answered Aug 19, 2009 at 20:08

swilliams

49.1k27 gold badges103 silver badges130 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Anders Over a year ago

Will I create this binder inside of its own file? If so, where should this be placed? In the same directory as my controllers? Thanks for the information and link!

Ben Robbins Over a year ago

I put my custom binders in a folder called Binders in the Models folder of my MVC Application.

swilliams Over a year ago

I generally create an Extensions folder in my project and put stuff like that and HtmlHelper extensions in there.

Craig Stuntz · Accepted Answer · 2009-08-19 20:32:41Z

1

The SQL Server EF provider in .NET 3.5 SP1 cannot retrieve server-generated GUIDs, since archaic versions of SQL Server couldn't support that. So you need to generate the GUID client-side, until this limitation is fixed.

You can do this in a model binder, as swilliams suggests, but IMHO binders should only bind data in the request. So I do it on my model tier. But either way will work.

answered Aug 19, 2009 at 20:32

Craig Stuntz

127k12 gold badges257 silver badges275 bronze badges

3 Comments

Anders Over a year ago

Could you elaborate on your method? As I am learning I would like to know all the options I have available to me. Thanks!

Craig Stuntz Over a year ago

Simple, really. I set the ID in code (with Guid.NewGuid()) before calling SaveChanges() when inserting a new record. All of this is done inside a model assembly which is separate from the assembly containing controllers and views.

Anders Over a year ago

So basically what I did, by removing the [Bind(Execute)] from the Movie parameter?

Sorantis · Accepted Answer · 2009-08-19 20:36:21Z

1

What is the type of ID field in SQL database? Is it uniqueidentifier? If not, change it to uniqueidentifier and make it autogenerated. Check out this article.

answered Aug 19, 2009 at 20:36

Sorantis

14.7k5 gold badges33 silver badges37 bronze badges

1 Comment

Craig Stuntz Over a year ago

He has already done that; read the question carefully. The SQL Server provider for the EF won't forward the autogenerated GUIDs to the client.

Arno 2501 · Accepted Answer · 2011-05-12 14:39:07Z

0

You could as well update your get Create Action as follow and give it the new guid at this point. Then it would be automatically transferred to the post action. The the all code would look like that :

public ActionResult Create()
{
   Movie movietocreate = new Movie();

   movietocreate.id = Guid.NewGuid();  //you set the new guid here

   return View(movietocreate);   
}

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(Movie movieToCreate)
{
    try
    {
        _entities.AddToMovieSet(movieToCreate);
        _entities.SaveChanges();

        return RedirectToAction("Index");
    }
    catch
    {
            return View();
    }
}

answered May 12, 2011 at 14:39

Arno 2501

9,5179 gold badges39 silver badges57 bronze badges

Collectives™ on Stack Overflow

Using a GUID as the ID in a database with ASP.NET MVC

4 Answers 4

3 Comments

3 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

3 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related