EditUI Complete

public string DisplayText 
{ 
  get
   { 
    return lblDisplayText.Text;
   }
   set
   {
    lblDisplayText.Text = value;
   }
  public object[] ListItems
        {
            get
            {
                object[] objRetVal = new object[lstboxValues.Items.Count];
                lstboxValues.Items.CopyTo(objRetVal, 0);
                return objRetVal;
            }
            set
            {
                lstboxValues.Items.AddRange(value);
            }
        }
private void btnAdd_Click(object sender, EventArgs, e)
  {
     string strInputText = txtInput.Text.Trim();
            int intValue = strInputText.IndexOfAny(new char[] { '<', '>', '/', '[', ']', ' ', '=' });
           if txtInput.Text.IndexofAny(cInvalid) < 0)
           { 
            if lstboxValues.Items.IndexOf(txtInput.Text) < 0
            {
              lstboxValues.Items.Add(txtInput.Text.Trim());
              txtInput.Text = "";
              btnAdd.Enabled = False;
            }
            else
            {
              MessageBox.Show
            }
private void lstboxValues_SelectedIndexChanged(object sender, EventArgs e)
{
  btnRemove.Enabled = false;
  if(lstboxValues.SelectedIndex >= 0)
    {
    btnRemove.Enabled = true;
    }
}
private void btnRemove_Click(object sender, EventArgs e)
{
  lstboxValues.Itmes.RemoveAt(lstboxValues.SelectedIndex);
}