title: How to get a list box to disallow duplicate items?
body: <p>Bassicly im creating a program that reads information from an xml file into a lisbox and allows the user to transfer items in the list box to another listBox. </p>
  
  <p>But i want to some how disallow multiple items from being imported from one listBox to the other. I thought i can somehow do an experession to check if the String already Exists in the listBox.</p>
  
  <p>The reason i want to do this is because the user can click x amount of times in order to import items and it's unproffesional.</p>
  
  <p>Any Help would be appreciated thank you.</p>
  
  <pre><code>private void button1_Click(object sender, EventArgs e)
  {
      if (!listBox.Items.Exists) // Random Idea which doesnt work
      {
          listBox2.Items.Add(listBox1.Items[listBox1.SelectedIndex]);
      }
  }
  </code></pre>