C#

private Students students;

public Students Students
{
    get{ return students; }
    set
    {
        students = value;
        txtName.Text = students.Name;
    }
}

Data datawindow = new Data();
datawindow.Students = stud;
datawindow.ShowDialog();

public Student EditStudent(Student input){
 this.firstNameTextBox.Text = input.FirstName;
 // ... etc to copy data into other controls
 // you could also use data binding
 if(DialogResult.OK == ShowDialog()){
  Student result = new Student();
  result.FirstName = firstNameTextBox.Text;
  // etc
  return result;
 } else return input;
}

public Student Student {
 get {
  Student student = new Student();
  student.FirstName = firstName.Text;
  // etc
  return student;
 }
 set {
  firstName.Text = value.FirstName;
  // etc
 }
}

studentDataForm.Student = someStudent;
if(DialogResult.OK == studentDataForm.ShowDialog(this)){
 // Do something with studentDataForm.Student to store the changed data
}

if (System.IO.File.Exists(physicalpath+filename))
   {
       System.IO.File.Delete(physicalpath+filename);
   }

btnSave.Click += new System.EventHandler(OnClick_Save);

using System;

public class EventRaisingClass
{
    // holds delegates to all subscribed methods
    public event EventHandler SomethingChanged;

    public void ChangeSomething()
    {
        //
        OnSomethingChanged(EventArgs.Empty);
    }

    protected virtual void OnSomethingChanged(EventArgs e)
    {
        EventHandler eh = SomethingChanged;
        if (eh != null)
            eh(this, e);
    }
}

using System;

public class SubscribingClass
{
    private EventRaisingClass eventRaisingInstance;

    public SubscribingClass()
    {
        eventRaisingInstance = new EventRaisingClass();
        // adds a delegate to the specified method to the event's invocation list
        eventRaisingInstance.SomethingChanged += EventRaisingInstanceSomethingChanged;
    }

    private void EventRaisingInstanceSomethingChanged(object sender, EventArgs e)
    {
        Console.WriteLine("Something Changed");
    }
    public void Update()
    {
        eventRaisingInstance.ChangeSomething();
    }
}