Procedura: aggiungere e modificare oggetti con ereditarietà tabella per tipo (Entity Framework)
In questo argomento viene utilizzato il modello EDM (Entity Data Model) definito in Procedura: definire un modello con ereditarietà tabella per tipo (Entity Framework). Viene illustrato come aggiungere un'istanza del tipo derivato in una gerarchia di ereditarietà tabella per tipo.
Per creare un progetto utilizzando l'ereditarietà tabella per tipo
Creare un progetto di applicazione console denominato SchoolDataClient e aggiungere riferimenti a System.Data.Entity e System.Runtime.Serialization.
Aggiungere un riferimento alla DLL compilata in base alla gerarchia di ereditarietà descritta in Procedura: definire un modello con ereditarietà tabella per tipo (Entity Framework).
Aggiungere gli schemi inclusi nell'argomento Procedura: definire un modello con ereditarietà tabella per tipo (Entity Framework) nella stessa cartella del file eseguibile di SchoolDataClient.
Aggiungere al progetto un file di configurazione dell'applicazione con il contenuto seguente.
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<connectionStrings><add name="SchoolDataLibContainer"
connectionString=
"metadata=res://*/SchoolDataLib.csdl|
res://*/SchoolDataLib.ssdl|
res://*/SchoolDataLib.msl;provider=System.Data.SqlClient;
provider connection string="
Data Source=localhost;
Initial Catalog=SchoolData;Integrated Security=True;
MultipleActiveResultSets=True""
providerName="System.Data.EntityClient" />
</connectionStrings>
</configuration>
Per aggiungere un'istanza del tipo derivato
Creare un'istanza del tipo DeptEngineering denominata newDept.
Inizializzare i dati delle proprietà di newDept.
Creare una nuova istanza del tipo Person.
Assegnare 3 alla proprietà PersonCategory per indicare la categoria Administrator.
Inizializzare le proprietà di newAdmin.
Assegnare il nuovo oggetto Person alla proprietà Administrator di newDept.
Aggiungere newDept e newAdmin all'archivio e salvare le modifiche.
Esempio
Option Explicit On
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Xml
Imports System.Xml.Linq
Imports System.Text
Imports SchoolDataLib
Module Module1
Sub Main()
Try
Using objectContext As SchoolDataLibContainer =
New SchoolDataLibContainer ()
' Display departments and administrators.
For Each dept As Department In objectContext.Departments
Console.WriteLine("School: {0} Budget: {1}", _
dept.Name, dept.Budget)
' Load associated contact reference if any.
dept.AdministratorReference.Load()
If dept.Administrator IsNot Nothing Then
Console.WriteLine("Administrator: {0} {1}", _
dept.Administrator.FirstName, _
dept.Administrator.LastName)
End If
Next
For Each eDept As DeptEngineering In _
objectContext.Departments.OfType(Of DeptEngineering)()
Console.WriteLine("{0} LabBudget: {1} FiberOp Budget: {2}", _
eDept.Name, eDept.LabBudget.ToString(), _
eDept.FiberOpticsBudget.ToString())
Next
Dim countDept As Integer = 0
Dim newDept As DeptEngineering = New DeptEngineering()
For Each dept As Department In objectContext.Departments
countDept = countDept + 1
Next
newDept.DepartmentID = countDept + 1
newDept.Name = "Engineering School " + (countDept + 1).ToString()
newDept.StartDate = DateTime.Now
newDept.FiberOpticsBudget = 250000.0
newDept.LabBudget = 400000.0
newDept.Budget = newDept.FiberOpticsBudget + newDept.LabBudget
' Create new contact item to be
' added as school administrator.
Dim countPerson As Integer = 0
For Each pers As Person In objectContext.People
countPerson = countPerson + 1
Next
Dim newAdmin As Administrator = New Administrator()
newAdmin.PersonID = countPerson + 1
newAdmin.FirstName = "Tony"
newAdmin.LastName = "Allen"
newAdmin.AdminDate = DateTime.Now - New TimeSpan(2000, 0, 0, 0)
' Assign the contact to Administrator property.
newDept.Administrator = newAdmin
' Add admin and school to object context.
objectContext.AddToPeople("People", newAdmin)
objectContext.AddToDepartments("Departments", newDept)
objectContext.SaveChanges()
End Using
Catch ex As System.Data.MappingException
Console.WriteLine(ex.ToString())
Catch ex As System.Data.CommandExecutionException
Console.WriteLine(ex.ToString())
Catch ex As System.Data.UpdateException
Console.WriteLine(ex.ToString())
End Try
End Sub
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using SchoolDataLib;
namespace SchoolDataClient
{
class Program
{
static void Main(string[] args)
{
try
{
using (SchoolDataLibContainer objectContext =
new SchoolDataLibContainer())
{
DeptEngineering newDept =
new DeptEngineering();
int countDept =
objectContext.Departments.Count<Department>();
newDept.DepartmentID = countDept + 1;
newDept.Name = "Engineering School " +
(countDept + 1).ToString();
newDept.StartDate = DateTime.Now;
newDept.FiberOpticsBudget = 250000.00M;
newDept.LabBudget = 400000.00M;
newDept.Budget = newDept.FiberOpticsBudget +
newDept.LabBudget;
// Create new contact item to be
// added as school administrator.
int countPerson = objectContext.People.Count<Person>();
Administrator newAdmin = new Administrator();
newAdmin.PersonID = countPerson + 1;
newAdmin.FirstName = "Jesper";
newAdmin.LastName = "Aaberg";
newAdmin.AdminDate = DateTime.Now -
new TimeSpan(2000, 0, 0, 0);
// Assign the contact to Administrator property.
newDept.Administrator = newAdmin;
// Add admin and school to object context.
objectContext.AddToPeople(newAdmin);
objectContext.AddToDepartments(newDept);
objectContext.SaveChanges();
}
}
catch (System.Data.MappingException e)
{
Console.WriteLine(e.ToString());
}
catch (System.Data.UpdateException e)
{
Console.WriteLine(e.ToString());
}
}
}
}
Vedere anche
Attività
Procedura: definire un modello con ereditarietà tabella per tipo (Entity Framework)
Procedura: creare ed eseguire query di oggetto utilizzando l'ereditarietà tabella per tipo (Entity Framework)