XML : Program failing when trying to use .Save() on XmlDocument after encryption

I'm working on a piece of code to access XML-files and encrypt some of the elements inside.

Mainly using example code from MSDN, and it seems to be working perfectly most of the way.

Here is my encryption method:

      public static bool EncryptionMethod(string path) {          // Testing Key generation - Rijndael is also known as the EAS-algorithm          RijndaelManaged key = null;            key = new RijndaelManaged();            // Create XmlDocument and populate with XML from chosen file/source          XmlDocument myXML = new XmlDocument();          myXML.PreserveWhitespace = true;          try          {              myXML.Load(path);          }          catch (System.IO.FileNotFoundException)          {              string exceptiontype = "The selected file was not found";              string caption = "File not found";              MessageBoxButton button = MessageBoxButton.OK;              MessageBoxImage icon = MessageBoxImage.Error;              MessageBoxResult result = MessageBox.Show(exceptiontype, caption, button, icon);              return false;          }            // Actual encryption magic          XmlElement elementToEncrypt = myXML.GetElementsByTagName("DataElement")[0] as XmlElement;          EncryptedXml eXml = new EncryptedXml();          byte[] encryptedElement = eXml.EncryptData(elementToEncrypt, key, false);          EncryptedData edElement = new EncryptedData();          // edElement.Type = EncryptedXml.XmlEncElementUrl;            // Setting the URI of the 256-bit AES algorithm          string algorithmOfEncryption = EncryptedXml.XmlEncAES256Url;          edElement.EncryptionMethod = new EncryptionMethod(algorithmOfEncryption);            edElement.CipherData.CipherValue = encryptedElement;          EncryptedXml.ReplaceElement(elementToEncrypt, edElement, false);            myXML.Save(path);            return true;      }    

But whenever I try to save the encrypted elements back to the original document with myXML.Save(path) I get a System.IO.IO.Exception with the reason that the file is used by another process.

The problem persists even if I create a new file or choose a different existing file.

What am I doing wrong?