title: How to get matched string from Regex? [C#]
body: <p>I have the following code:</p>
  
  <pre><code>private void button_borrow_Click(object sender, EventArgs e)
      {
          Regex filter = new Regex(@"[0-9]*");
          String items = "";
          var selectedItems = checkedListBox_bookview.CheckedItems;
          foreach (var item in selectedItems)
          {
  
          }
          MessageBox.Show(items.ToString() + " Were selected: " + selectedItems.Count);
      }
  </code></pre>
  
  <p>I want to get the matched Strings from <code>filter</code>. how do I do so?</p>