/// <summary>
/// This method demonstrates how to undo the changes in Entity level using DbContext.
/// </summary>
public static void UndoChangesInEntity()
{
using (DbMySchool school = new DbMySchool())
{
DbDepartment department = school.DbDepartments.FirstOrDefault();
IQueryable <DbCourse> courses = from c in school.DbCourses
where c.DepartmentID == department.DepartmentID
select c;
Console.WriteLine("Before changes:");
foreach (DbCourse course in courses)
{
course.ShowDbCourse();
}
// Change the courses.
Console.WriteLine("After changes:");
foreach (DbCourse course in courses)
{
course.Title += "-Modified";
course.ShowDbCourse();
}
Console.WriteLine("After Undo the First Course Entity:");
// Undo one course. You can see only the changes of the first course are undone.
school.UndoDbEntity(courses.FirstOrDefault());
foreach (DbCourse course in courses)
{
course.ShowDbCourse();
}
}
}
/// <summary>
/// This method demonstrates how to undo the changes in Entities level using DbContext.
/// </summary>
public static void UndoChangesInEntities()
{
using (DbMySchool school = new DbMySchool())
{
DbDepartment department = school.DbDepartments.FirstOrDefault();
IQueryable <DbCourse> courses = from c in school.DbCourses
where c.DepartmentID == department.DepartmentID
select c;
Console.WriteLine("Before changes:");
foreach (DbCourse course in courses)
{
course.ShowDbCourse();
}
// Change the department and the related courses.
Console.WriteLine("After changes:");
department.Name += "-Modified";
foreach (DbCourse course in courses)
{
course.Title += "-Modified";
course.ShowDbCourse();
}
Console.WriteLine("After Undo Course Entities:");
// Undo the DbCourse type Entities. We will see the changes of the department
// are not undone.
school.UndoDbEntities <DbCourse>();
foreach (DbCourse course in courses)
{
course.ShowDbCourse();
}
}
}
/// <summary>
/// This method demonstrates how to undo the changes in Property level using DbContext.
/// </summary>
public static void UndoChangesInProperty()
{
using (DbMySchool school = new DbMySchool())
{
DbCourse course = school.DbCourses.FirstOrDefault();
DbDepartment department = school.DbDepartments.FirstOrDefault();
if (course != null)
{
Console.WriteLine("Before changes:");
course.ShowDbCourse();
Console.WriteLine("After changes:");
// Change the course Properties.
course.Title += "-Modified";
course.Department = department;
course.ShowDbCourse();
Console.WriteLine("After Undo Course Entity's Title Property:");
// Undo the change in the Entity Property level. UndoDbEntityProperty
// method will undo the Title property of the course, but the change of the
// Department Property will not be undone.
school.UndoDbEntityProperty(course, "Title");
course.ShowDbCourse();
}
}
}
/// <summary>
/// This method demonstrates how to undo the changes in Context level using DbContext.
/// </summary>
public static void UndoChangesInContext()
{
using (DbMySchool school = new DbMySchool())
{
DbCourse course = school.DbCourses.FirstOrDefault();
if (course != null)
{
Console.WriteLine("Before changes:");
course.ShowDbCourse();
Console.WriteLine("After changes:");
// Change the course and the related department.
course.Title += "-Modified";
course.Department.Name += "-Modified";
course.ShowDbCourse();
Console.WriteLine("After Undo DbContext:");
// Undo the whole Context.
school.UndoDbContext();
course.ShowDbCourse();
}
}
}
