At the beginning of the code file for the

CourseViewer

form, add the following

using

(C#) or

Imports

(Visual Basic) statements to reference the model created from the School database and the entity namespace.

Visual Basic

Imports System.Data.Objects
Imports System.Data.Objects.DataClasses

C#

using System.Data.Objects;
using System.Data.Objects.DataClasses;

At the top of the partial class definition for the

CourseViewer

form, add the following code that creates an

ObjectContext

instance.

Visual Basic

' Create an ObjectContext instance based on SchoolEntity.
Private schoolContext As SchoolEntities

C#

// Create an ObjectContext instance based on SchoolEntity.
private SchoolEntities schoolContext;

In the

CourseViewer

form designer, double-click the

CourseViewer

form. This opens the code page for the form and creates the

courseViewer _Load

event handler method.

In the

courseViewer _Load

event handler method, copy and paste the following code that defines the

DataGridView

, executes a query that returns a collection of departments (ordered by

Name

), and binds the collection of

Department

objects to the departmentList control.

Visual Basic

' Initialize the ObjectContext.
schoolContext = New SchoolEntities()

' Define a query that returns all Department objects and related
' Course objects, ordered by name.
Dim departmentQuery As ObjectQuery(Of Department) = _
    schoolContext.Department.Include("Course").OrderBy("it.Name")

Try
    ' Bind the ComboBox control to the query, which is
    ' executed during data binding.
    Me.departmentList.DisplayMember = "Name"
    Me.departmentList.DataSource = departmentQuery
Catch ex As Exception
    MessageBox.Show(ex.Message)
End Try

C#

// Initialize the ObjectContext.
schoolContext = new SchoolEntities();

// Define a query that returns all Department objects and related
// Course objects, ordered by name.
ObjectQuery<Department> departmentQuery =
    schoolContext.Department.Include("Course").OrderBy("it.Name");

try
{
    // Bind the ComboBox control to the query, which is
    // executed during data binding.
    this.departmentList.DisplayMember = "Name";
    this.departmentList.DataSource = departmentQuery;
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}

In the

CourseViewer

form designer, double-click the

departmentList

control. This creates the

departmentList_SelectedIndexChanged

event handler method.

Paste the following code that loads the courses that are related to the selected department.

Visual Basic

Try
    ' Get the object for the selected department.
    Dim department As Department = _
        CType(Me.departmentList.SelectedItem, Department)

    ' Bind the grid view to the collection of Course objects
    ' that are related to the selected Department object.
    courseGridView.DataSource = department.Course

    ' Hide the columns that are bound to the navigation properties on Course.
    courseGridView.Columns("Department").Visible = False
    courseGridView.Columns("CourseGrade").Visible = False
    courseGridView.Columns("OnlineCourse").Visible = False
    courseGridView.Columns("OnsiteCourse").Visible = False
    courseGridView.Columns("Person").Visible = False

    courseGridView.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells)
Catch ex As Exception
    MessageBox.Show(ex.Message)
End Try

C#

try
{
    // Get the object for the selected department.
    Department department =
        (Department)this.departmentList.SelectedItem;

    // Bind the grid view to the collection of Course objects
    // that are related to the selected Department object.
    courseGridView.DataSource = department.Course;

    // Hide the columns that are bound to the navigation properties on Course.
    courseGridView.Columns["Department"].Visible = false;
    courseGridView.Columns["CourseGrade"].Visible = false;
    courseGridView.Columns["OnlineCourse"].Visible = false;
    courseGridView.Columns["OnsiteCourse"].Visible = false;
    courseGridView.Columns["Person"].Visible = false;

    courseGridView.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells);
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}