Persistence database entity framework problem and WPF

Question

Hi,

I'm a newbie of database concept and Entity Framework. I'm creating a small application with the WPF technology; in this application I use a main window to display the datas that I can add with another window dialog. These datas are introduced in a database (based to service) by various textboxes. Below my database structure:

I populate my database with this code in my dialog window:

 

dbDistintaEntities distinta = new dbDistintaEntities();
Societa soc = new Societa(){ 
                ID = 1,
                Nome = this.SquadraNome, 
                Campo = this.SquadraCampo,
                Presidente = this.SquadraPres,
                Allenatore = this.SquadraAll,
                DirigenteAcc = "ilnulla",
                DirigenteAr = "ilnulla",
                Massaggiatore = "ilnulla",
                Medico = "ilnulla",
            };
this.distinta.AddToSocieta(soc);
this.distinta.SaveChanges();

 

So I can retrieve the previous datas in a main window with this code:

 

dbDistintaEntities distinta = new dbDistintaEntities();

var societa = distinta.Societa.ToList().Last();
SquadraNome = societa.Nome;

 

 

This implementation works well when I retrieve the datas when I return from dialog window while application is running but if I put the same code to retrieve the datas in a constructor of main window to load the data when the application is started I receive this error:

'The invocation of the constructor on type 'DistintaProject.Views.MainWindow' that matches the specified binding constraints threw an exception.' Line number '6' and line position '9'.

I think that the problem is due to database is empty. To manage the window I use an Unity Container (to agree at MVVM pattern), I don't think that is a problem.

I don't understanding, anyone could help me?

 

Thank you!

LUCA