EntityFramework 6.0.0.0 reads data, but it is not inserting

I've created a Service-based Database folderName->Add New Item->Data->Service-based Database file into WPF application. Then I've used Database First approach and have created the PersonsModel.edmx file. These operations are executed perfectly.

The reading of data works okay:

using (PersonDBEntities db = new PersonDBEntities())
{
   string dep = (db.Departament.FirstOrDefault()).DepName;//data can be read perfectly
   string bureau = (db.Bureau.FirstOrDefault()).BureauName;//data can be read perfectly 
}

However, data can not be inserted(this code works in other projects very well) :

using (PersonDBEntities db = new PersonDBEntities())
{
   try 
   {
      Departament dep = new Departament() { DepName = "NewDep" };
      db.Departament.Add(dep);
      db.SaveChanges();
   }
   catch(Exception ex)
   {
      string message = ex.Message;
   }                
 }

Does anybody know why data is not inserted?

No errors, exceptions, just EF is not writing data.

I've upload a project to github, maybe it can be interesting to see:).

A SQL query to create a table:

CREATE TABLE [dbo].[Departament] (
    [IdDep]   INT            IDENTITY (1, 1) NOT NULL,
    [DepName] NVARCHAR (100) NULL,
    PRIMARY KEY CLUSTERED ([IdDep] ASC)
);

and EF model class:

public partial class Departament
{
    public Departament()
    {
        this.Person = new HashSet<Person>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)] 
    public int IdDep { get; set; }
    public string DepName { get; set; }

    public virtual ICollection<Person> Person { get; set; }
}

What Console of Visual Studio 2013 outputs:

Started transaction at 18.09.2016 1:34:15 +03:00

INSERT [dbo].Departament VALUES (@0) SELECT [IdDep] FROM [dbo].[Departament] WHERE @@ROWCOUNT > 0 AND [IdDep] = scope_identity()

-- @0: '311' (Type = String, Size = 100)

-- Executing at 18.09.2016 1:34:15 +03:00

-- Completed in 79 ms with result: SqlDataReader

Committed transaction at 18.09.2016 1:34:15 +03:00

Closed connection at 18.09.2016 1:34:15 +03:00

If I run the above query as a SQL database query in Visual Studio 2013, then it inserts data perfectly.

I've tried the following approaches in sequential order:

//db.Departament.Add(dep);//not working
//db.Entry(dep).State = EntityState.Added;//not working
//db.Departament.Attach(dep);//not working
//db.Entry(dep).State = dep.IdDep == 0 ? EntityState.Added : EntityState.Modified;//not working
//db.Departament.Attach(dep);//not working
db.Entry(dep).State = EntityState.Modified;//not working