Public object to be used in Form.

public partial class Form1 : Form
 {
  public Form1()
  {
   InitializeComponent();
  }

  private void button1_Click(object sender, EventArgs e)
  {
   ContactManager mngr = new ContactManager();
   string currContact;

   try
   {
    currContact = listBox.SelectedItem.ToString();
    bool flg = mngr.RemoveCondact(currContact);
    if (flg )
     MessageBox.Show("Successfully Removed");
   }
   
   catch (Exception)
   { return; }
   
  
  }
 }
 class ContactManager
 {
  private List m_contactRegistry; //declare object of the collection
  public ContactManager()
  {
   m_contactRegistry = new List();
  }
  ///

  /// returns the count of m_contactRegistry
  ///

  ///
  ///
  public Contact GetContact(int index)
  {
   if (index < 0 || index >= m_contactRegistry.Count)
    return null;
   return m_contactRegistry[index];
  }
  public bool RemoveCondact(string str)
  {
   foreach (Contact c in m_contactRegistry)
   {
    if (c.ToString() == str)
    {
     m_contactRegistry.Remove(c);
     return true;
    }
   }
   return false;
  }
 }
 public class Contact
 {

 }