merge multi xml file to xml

XmlUtils

/// <summary>
    /// 
    /// </summary>
    public static class XmlUtils
    {
        /// <summary>
        /// MergeFiles to a single file
        /// </summary>
        /// <param name="files"></param>
        /// <param name="fileContentMergeFail"></param>
        /// <returns></returns>
        public static string MergeFiles(List<string> files)
        {
            XmlDocument doc = new XmlDocument();
            if (files.Count > 0)
            {
                string fileToMerge = null;
                for (int i = 0; i < files.Count; i++)
                {
                    fileToMerge = files[i];

                    if (!File.Exists(fileToMerge))
                    {
                        throw new FileNotFoundException(fileToMerge);
                    }

                    if (doc.DocumentElement == null)
                    {
                        doc.Load(fileToMerge);
                    }
                    else
                    {
                        XmlDocument docTemp = new XmlDocument();
                        docTemp.Load(fileToMerge);
                        foreach (XmlNode node in docTemp.DocumentElement.ChildNodes)
                        {
                            XmlNode nodeTemp = doc.ImportNode(node, true);
                            doc.DocumentElement.AppendChild(nodeTemp);
                        }
                    }
                }
            }

            return doc.OuterXml;
        }
       
    }