/* Indexator which gets and sets an element
* at a specified index.
*/
public Student this[int index]
{
get
{
try
{
return(students.ElementAt(index));
}
catch (ArgumentOutOfRangeException ex)
{
return(null);
}
}
set
{
if (index >= 0 & index < students.Count)
{
students[index] = value;
StudentListEventHandlerEventArgs args = new StudentListEventHandlerEventArgs();
args.ChangedObject = students[index];
args.ChangeType = "An element was changed.";
args.CollectionName = this.CollectionName;
OnStudentReferenceChanged(args);
}
}
}
/* Abstraction method to separate event handler call */
protected virtual void OnStudentReferenceChanged(StudentListEventHandlerEventArgs args)
{
StudentListHandler handler = StudentReferenceChanged;
if (handler != null)
{
handler(this, args);
}
}
/* Adds 5 default Student objects to students collection */
public void AddDefaults()
{
if (students == null)
{
students = new List <Student>();
}
for (int i = 0; i < 5; i++)
{
Student stud = new Student();
students.Add(stud);
StudentListEventHandlerEventArgs args = new StudentListEventHandlerEventArgs();
args.ChangedObject = stud;
args.ChangeType = "A new default Student object was added to collection.";
args.CollectionName = this.CollectionName;
OnStudentsCountChanged(args);
}
}
public void AddStudents(params Student[] student_array)
{
if (student_array != null)
{
if (this.students == null)
{
this.students = new List <Student>();
}
for (int i = 0; i < student_array.Length; i++)
{
this.students.Add(student_array[i]);
StudentListEventHandlerEventArgs args = new StudentListEventHandlerEventArgs();
args.ChangedObject = student_array[i];
args.ChangeType = "A new Student object from a source was added to collection.";
args.CollectionName = this.CollectionName;
OnStudentsCountChanged(args);
}
}
}
/* Removes an element from collection.
* Returns "false" if there is no element with
* specified index.
*/
public bool Remove(int j)
{
Student stud = new Student();
try
{
stud = students.ElementAt <Student>(j);
students.RemoveAt(j);
}
catch (ArgumentOutOfRangeException ex)
{
return(false);
}
StudentListEventHandlerEventArgs args = new StudentListEventHandlerEventArgs();
args.ChangedObject = stud;
args.ChangeType = "A Student at index " + j + " was removed from collection.";
args.CollectionName = this.CollectionName;
OnStudentsCountChanged(args);
return(true);
}
/* Event handler for StudentReferenceChanged event from StudentCollection. */
public void handle_StudentReferenceChanged(object sender, StudentListEventHandlerEventArgs args)
{
JournalEntry je = new JournalEntry(args.CollectionName, args.ChangeType, args.ChangedObject.ToString());
entries.Add(je);
}
