Understanding C# Events use of sender object

Question

I am reasonably new to C# as a language (coming from a C++ background) and I am currently in the process of writing an application that makes use of an event driven API.

Answer 1

When parameters are passed by reference,

1. The properties present inside the reference instance can be change without affecting the original reference instance.

2. Original reference can be changed using the ref keyword.

The following is an example

public partial class ParentForm : Form
{
    public ParentForm()
    {
        InitializeComponent();
        ChildForm childForm = new ChildForm();
        ChangeCaption( childForm );
        //Will display the dialog with the changed caption.
        childForm.ShowDialog();
        ChangeCaption( ref childForm );
        //Will give error as it is null
        childForm.ShowDialog();
    }

    void ChangeCaption( ChildForm formParam )
    {
        // This will change openForm’s display text
        formParam.Text = "From name has now been changed";
        // No effect on openForm
        formParam = null;                        
    }


    void ChangeCaption( ref ChildForm formParam )
    {
        // This will change openForm’s display text
        formParam.Text = "From name has now been changed";
        // This will destroy the openForm variable!
        formParam = null;                        
    }
}