I have a simple xml document and I want to get the count of a certain node. How can I do this? Right now I am using the following syntax to get the node.

```
  // send request and strore in xpath doc (read-only)
    XPathDocument xDoc = new XPathDocument(requestURL);

    // Create navigator  
    XPathNavigator navigator = xDoc.CreateNavigator();

    XPathNavigator navError = navigator.SelectSingleNode("/api/error");

```