SaveChanges is not working in all my project?

Question

I working with a local database on an ASP.NET MVC project using Visual Studio.

I'm having trouble modifying the database. When I call SaveChanges() I always get this error:

The value cannot be null Parameter Name: Source

Here's an example of how I modify the database, and the error log / StackTrace.

 [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult CreateMedico(Medico medicoToCreate)
    {
        List<Medico> dedo = data.Medico.ToList();
        if (ModelState.IsValid)
        {
            using (MedsEntities data = new MedsEntities())
            {
                medicoToCreate.Id = dedo.Count() + 1;
                data.Medico.Add(medicoToCreate);
  System.Diagnostics.Debug.WriteLine("RECURSO :" + medicoToCreate.RECURSO_MEDICO);
                    System.Diagnostics.Debug.WriteLine("NOMBRE: " + medicoToCreate.NOMBRE);
                    System.Diagnostics.Debug.WriteLine("TIPO: " + medicoToCreate.TIPO);
                // and so on with all properties.....
                System.Diagnostics.Debug.WriteLine("MEDICO A GRABAR:" + medicoToCreate.NOMBRE);
                if (medicoToCreate == null)
                {
                    System.Diagnostics.Debug.WriteLine("MEDICOTOCREATE, IS NULL");

                }
                else {
                    System.Diagnostics.Debug.WriteLine("MEDICOTOCREATE, IS NOT NULL");
                }
                data.SaveChanges();
                return RedirectToAction("MedicosList");
            }
        }

        return RedirectToAction("MedicosList");
    }

Stack trace:

   en System.Data.Entity.Internal.InternalContext.SaveChanges()
   en System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
   en System.Data.Entity.DbContext.SaveChanges()
   en FINAL.Controllers.HomeController.CreateMedico(Medico medicoToCreate) en d:\IDEX8544 KARLO\Documents\Visual Studio 2012\Projects\FINAL\FINAL\Controllers\HomeController.cs:línea 70
   en lambda_method(Closure , ControllerBase , Object[] )
   en System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
   en System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   en System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   en System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41()
   en System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _)
   en System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   en System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   en System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33()
   en System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49(

Connection Strings (Thanks Oleg):

 <connectionStrings>
    <add name="MedsEntities" connectionString="metadata=res://*/Models.ModelMeds.csdl|res://*/Models.ModelMeds.ssdl|res://*/Models.ModelMeds.msl;provider=System.Data.SqlServerCe.4.0;provider connection string=&quot;data source=|DataDirectory|\DB.sdf&quot;" providerName="System.Data.EntityClient" />
    <add name="HospitalEntities" connectionString="metadata=res://*/Models.ModelHosp.csdl|res://*/Models.ModelHosp.ssdl|res://*/Models.ModelHosp.msl;provider=System.Data.SqlServerCe.4.0;provider connection string=&quot;data source=|DataDirectory|\DB.sdf&quot;" providerName="System.Data.EntityClient" />
    <add name="LabsEntities" connectionString="metadata=res://*/Models.ModelLabs.csdl|res://*/Models.ModelLabs.ssdl|res://*/Models.ModelLabs.msl;provider=System.Data.SqlServerCe.4.0;provider connection string=&quot;data source=|DataDirectory|\DB.sdf&quot;" providerName="System.Data.EntityClient" />
    <add name="FarmaciasEntities" connectionString="metadata=res://*/Models.ModelFarms.csdl|res://*/Models.ModelFarms.ssdl|res://*/Models.ModelFarms.msl;provider=System.Data.SqlServerCe.4.0;provider connection string=&quot;data source=|DataDirectory|\DB.sdf&quot;" providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

MEDICO MODEL:

namespace FINAL.Models
{
    using System;
    using System.Collections.Generic;

    public partial class Medico
    {
        public string RECURSO_MEDICO { get; set; }
        public string NOMBRE { get; set; }
        public string TIPO { get; set; }
        public string TIPO2 { get; set; }
        public string TIPO3 { get; set; }
        public string CELULAR { get; set; }
        public string EMAIL { get; set; }
        public string TEL1 { get; set; }
        public string TEL2 { get; set; }
        public string EXT { get; set; }
        public string HOSPITAL { get; set; }
        public string DIRECCION { get; set; }
        public string LAT { get; set; }
        public string LON { get; set; }
        public string C33DIGITOS { get; set; }
        [Key]
        public int Id { get; set; }
    }
}

DB Model:

namespace FINAL.Models
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;

    public partial class MedsEntities : DbContext
    {
        public MedsEntities()
            : base("name=MedsEntities")
        {
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }

        public DbSet<Medico> Medico { get; set; }
    }
}

Im pretty new In MVC .NET, and database management, if Im using a local database, my conection string is where I call it (the DB)? — Karlo A. López, Jun 11 '15 at 23:20
Its a DB Model, which exactly would be the definition? Or you mean `medicoToCreate`?? — Karlo A. López, Jun 11 '15 at 23:36
medicoToCreate is variable of Medico type, I want to see db model class and Medico class — Oleg, Jun 11 '15 at 23:43
I think that problem is that your entity Medico doesn't have a key. Try to add Key attribute on key property. — Oleg, Jun 11 '15 at 23:51
You mean to put `[Key]` into the top of `Medico`? Or create a new column in table named "Key" and to be an int? — Karlo A. López, Jun 12 '15 at 00:04
I just added a Key attribute with key property, nothing happened — Karlo A. López, Jun 12 '15 at 18:07
Why are over overriding `OnModelCreating` only to throw an exception? This may be your problem, if not, it's just an error waiting to happen (99% chance this is your error or part of it) — Dave Alperovich, Jun 14 '15 at 18:31
Are you able to retrieve data from your database? So is your connection string working for other actions like selects? — Dacker, Jun 14 '15 at 22:57

score 2 · Accepted Answer · answered Jun 15 '15 at 04:20

You are getting this exception because some of your Model property has null value. But before checking this i would recommend you that you make a key column in your model and it shouldn't be Nullable. And when you add a new object of your model value of the key column should be set before calling SaveChanges.

You key column should be like this

[Key]
public int Id { get; set; }

If you don't want to manually set the value of this key column when adding a new object you can make it identity column so its value will be inserted automatically for this you have to add [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)] to your key column.

[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }

And make sure when you add a new object all of your properties have the value otherwise you will get the same exception.

Thanks for answering, now Im printing in console all the properties of `MedicoTocreate` and all the database has the Id property (Not allowing nulls) and every time I add a new entry I add also the `Id` property but the error persist!!!! Thanks. I will update my question with my new code. — Karlo A. López, Jun 15 '15 at 16:41

Dacker · Answer 2 · 2015-06-14T23:18:26.377

1

There is a variety of issues that will result in this errorMessage in EF.

As far as I remember is that Entity Framework relies on your object having some unique identifier. The easiest way to have one is the Id you have, but you shouldn't make it nullable. It should be of type int and your SQL Server should have identity set to true for this column.

If this is not your issue, debug and check which values are set and more important which are still null before SaveChanges is called.

edited Jun 14 '15 at 23:18

answered Jun 14 '15 at 22:56

Dacker

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2
8
12

If it's not your id, then debug and check all the values. Is one of the properties that will get persisted to the database still null? – Dacker Jun 15 '15 at 18:57
Check my question, Im debugging all values and they all are being printed correctly. Including the ID – Karlo A. López Jun 15 '15 at 18:58
Are you providing an answer or just general advice? Your points are good, but nothing seems close to a solution. "beware of this", and "try that" are appropriate as comments. – Dave Alperovich Jun 15 '15 at 19:01
I saw you printing to console, but not what the result was. If you print the values, do all properties have values? Or are some "empty"? NULL values printed to console might be printed as empty too. That's why setting a breakpoint and checking the object in locals might be better. Something has to be null. – Dacker Jun 15 '15 at 19:02
@DaveAlperovich I am trying to give the OP an answer since he is asking for help, why he is getting the error. The error message is a general errorMessage that can be caused by several issues. That's why I am trying to explain the 2 causes that are most likely for his situation. – Dacker Jun 15 '15 at 19:14
Dacker, help is admirable. Pointers are helpful. I understand the OP has asked for advice, but advice does not constitute an answer. Pointers and advice on what it could be are the purpose of comments. Answers are solutions. – Dave Alperovich Jun 15 '15 at 19:19

score 1 · Answer 3 · edited May 23 '17 at 12:30

1

Does it work if you remove your Bind(Exclude = "Id") attribute?

That appears to be the culprit. It looks like you're using it on a DomainModel instead of a ViewModel. You're trying to set it after the fact, but the attribute is already set.

There are a few ways around this.

Create a ViewModel that only has the properties you wish to be editable, and then pass that back and map to your DomainModel.
Let your database handle the auto increments
Simply remove the Bind(Exclude = "Id") attribute and don't expose that property (like above)

You're ultimately trying to insert without an Identifier.

You can see this answer here that has some more detail on it: Alternative for [Bind(Exclude = “Id”)]

edited May 23 '17 at 12:30

Community

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1

answered Jun 15 '15 at 20:02

ragerory

1,360
1
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Thanks, I have removed the `Bind(Exclude = "Id")` tag and nothing happened, Im still getting the error. Thanks. – Karlo A. López Jun 15 '15 at 21:25
What about the other options? Have you checked the call stack? You should be able to monitor that and see what query is being generated and that should give you more insight as to what piece is incorrect. – ragerory Jun 16 '15 at 13:30

SaveChanges is not working in all my project?

3 Answers3