Delete line string in Isolated Storage text file.

I read text file in Isolated Storage and I select myList. But I want to delete it.
How to delete string line.

                                                                                                                              


StreamReader reader = new StreamReader(new IsolatedStorageFileStream(strFileName, FileMode.Open, isoStore));     string rawData = reader.ReadToEnd();     reader.Close();      string[] sep = new string[] { "\r\n" };     string[] arrData = rawData.Split(sep, StringSplitOptions.RemoveEmptyEntries);      List myContact = new List();     foreach (var strLine in arrData) {     myContact.Add(new Message(strLine.ToString()));     }      this.myList.ItemsSource = myContact;

private void listF_select(object sender, SelectionChangedEventArgs e)
        {
            if (listFr.SelectedItem != null)          
              {  
               IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication();
                string strFileName = "/FavoriteList.txt";
                string strline = listFr.SelectedItem.ToString();
                StreamReader reader = strline(new IsolatedStorageFileStream(strFileName, FileMode.Open, isoStore));
                ClearValue.
                Close();
                
            }
            else
            {
                MessageBox.Show("eeeeeeeeeeeeeeeeeee");
            }

        }