title: Dont add duplicate objects into List
body: <p>I cant seem to find a way not to add objects into my list that are the same, I tried .Contains but I just did not get it to work, any other workarounds? I believe I must use a if statement, and have the creation of the object in the else, but how do I do in the if statement?</p>
  
  <pre><code>public Form1()
      {
          InitializeComponent();
      }
      private const string filnamn = "kontakter.bin";
      Kontakter kontakt;
      private List&lt;Kontakter&gt; kontakter;
  
  
      private void buttonLagra_Click(object sender, EventArgs e)
      {
              Kontakter nyKontakt = new Kontakter();
              {
                  nyKontakt.Telefonnr = textBoxTelefonnr.Text;
                  nyKontakt.Namn = textBoxNamn.Text;
              }
  
              kontakter.Add(nyKontakt);
              listBox1.DataSource = null;
              listBox1.DataSource = kontakter;
              BinaryFormatter bf = new BinaryFormatter();
              FileStream fs = new FileStream(filnamn, FileMode.OpenOrCreate, FileAccess.Write);
              bf.Serialize(fs, kontakter);
              fs.Close();
          }
  </code></pre>