Extension method to output xml declaration with tostring

XDocumentExtensions.cs

using System.IO;
using System.Text;
using System.Xml.Linq;

    /// <summary>
    /// Extension methods on the XDocument class.
    /// </summary>
    internal static class XDocumentExtensions
    {
        /// <summary>
        /// The normal ToString does not return the Xml Declaration line. 
        /// This one allows you to specify if you want it or not.
        /// </summary>
        /// <param name="doc">The XDocument to return as a string</param>
        /// <param name="includeXmlDeclaration">When true the Xml Declaration will be included.</param>
        /// <returns>The string representation of the xml document encoded as UTF8 </returns>
        public static string ToString(this XDocument doc, bool includeXmlDeclaration)
        {
            return ToString(doc, includeXmlDeclaration, Encoding.UTF8);
        }

        /// <summary>
        /// The normal ToString does not return the Xml Declaration line. This one allows you to specify if you want it or not.
        /// </summary>
        /// <param name="doc">The XDocument to return as a string</param>
        /// <param name="includeXmlDeclaration">When true the Xml Declaration will be included.</param>
        /// <param name="encoding">The string encoding to use</param>
        /// <returns>The string representation of the xml document</returns>
        public static string ToString(this XDocument doc, bool includeXmlDeclaration, Encoding encoding)
        {
            if (!includeXmlDeclaration)
                return doc.ToString();

            using (var sw = new MemoryStream())
            using (var strw = new StreamWriter(sw, encoding))
            {
                doc.Save(strw);
                return encoding.GetString(sw.ToArray());
            }
        }
    }