public MessHist(ContactForm cnt, List<MyDict> l)
{
InitializeComponent();
this.cnt = cnt;
list = l;
MessageHist();
this.textBox2.Text = mainstr;
}
// тут все ясно
private void ContactBox_SelectedIndexChanged(object sender, EventArgs e)
{
int index = ContactListBox.SelectedIndex;
ContactForm Contact = new ContactForm(this, users[index], mainUser.ListReturner(users[index].firstname));
Contact.Show();
}