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How to: Add and Modify Objects with Table-per-Hierarchy Inheritance (Entity Framework)

This example uses the Entity Data Model (EDM) designed in the topic How to: Define a Model with Table-per-Hierarchy Inheritance (Entity Framework).

To create a project using the Table-Per-Hierarchy inheritance model

  1. Create a console application project and add references to System.Data.Entity and System.Runtime.Serialization.

  2. Add a reference to the dll built from the inheritance model in the topic How to: Define a Model with Table-per-Hierarchy Inheritance (Entity Framework).

  3. Add the schemas from the topic How to: Define a Model with Table-per-Hierarchy Inheritance (Entity Framework) to the same folder as the SchoolDataClient executable.

  4. Add an application configuration file with content as shown in the following example.

    <?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=&quot;
       Data Source=localhost;
       Initial Catalog=SchoolData;Integrated Security=True;
       MultipleActiveResultSets=True&quot;" 
       providerName="System.Data.EntityClient" />
      </connectionStrings>
    </configuration>
    

To add new Instructor and Student derived types and modify Instructor

  1. Instantiate the SchoolDataEntities object context.

  2. Create a new instance of the Instructor type and assign data to Instructor properties.

  3. Add the new instance of Instructor to storage using the AddToPeople method. The parameter of the AddToPeople method is the name of the new Instructor instance.

  4. Save changes.

  5. Create a new instance of the Student type and initialize properties.

  6. Add to storage, and save changes.

  7. Create an ObjectParameter to be used in a query for an Instructor instance with the property LastName equal to Griffin.

  8. Test the query to verify that the Instructor with this property exists in storage.

  9. Query for the designated Instructor and assign it to a variable named changeInstructor.

  10. Assign the property LastName to Anderson, and save changes.

Example

The following code adds a new instance of the Instructor type and the Student type. Next it queries for an Instructor for LastName Griffin and changes the LastName property to Anderson.

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(newAdmin)
                objectContext.AddToDepartments(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
End Module
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using SchoolDataLibTPH;
using System.Data.Objects;
namespace SchoolDataLib
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                // Add new Instructor.
                using (SchoolDataLibContainer objectContext =
                                      new SchoolDataLibContainer())
                {
                    Instructor newInstructor =
                        new Instructor();
                    newInstructor.PersonID =
                            objectContext.People.Count<Person>() + 1;
                    newInstructor.FirstName = "Satomi";
                    newInstructor.LastName = "Hayakawa";

                    newInstructor.HireDate = DateTime.Now;

                    objectContext.AddToPeople(newInstructor);
                    objectContext.SaveChanges();

                    // Add new Student.
                    Student newStudent = new Student();
                    int count = objectContext.People.Count<Person>();
                    newStudent.PersonID = count + 1;
                    newStudent.FirstName = "Uzi";
                    newStudent.LastName = "Hefetz";
                    newStudent.EnrollmentDate = DateTime.Now;


                    objectContext.AddToPeople(newStudent);
                    objectContext.SaveChanges();

                    // Change the last name of an instructor.
                    ObjectParameter param =
                                  new ObjectParameter("p", "Hayakawa");
                    if (0 != objectContext.People.OfType<Instructor>().
                                  Where("it.LastName = @p",
                                  param).Count<Instructor>())
                    {
                        Instructor changeInstructor = 
                              objectContext.People.
                              OfType<Instructor>().Where(
                             "it.LastName = @p", param).First();
                        changeInstructor.LastName = "Anderson";
                        objectContext.SaveChanges();

                    }

                    objectContext.Connection.Close();
                }
            }

            catch (System.Data.MappingException e)
            {
                Console.WriteLine(e.ToString());
            }
            catch (System.Data.UpdateException e)
            {
                Console.WriteLine(e.ToString());
            }

        }
    }
}

See Also

Tasks

How to: Define a Model with Table-per-Hierarchy Inheritance (Entity Framework)
How to: Create and Execute Object Queries using Table-per-Hierarchy Inheritance (Entity Framework)