XmlHelper.cs

        public class XMLHelper
        {
            public static string Serialize(T entity, Encoding encoding = null)
            {
                StringBuilder sb = new StringBuilder();
                XmlSerializer serializer = new XmlSerializer(typeof(T));

                if (encoding == null)
                {
                    using (TextWriter tw = new StringWriter(sb))
                        serializer.Serialize(tw, entity);
                    return sb.ToString();
                }

                using (MemoryStream ms = new MemoryStream())
                using (StreamWriter sw = new StreamWriter(ms, encoding))
                {
                    serializer.Serialize(sw, entity);
                    byte[] bytes = ms.ToArray();
                    return encoding.GetString(bytes, 0, bytes.Length);
                }
            }

            public static void AppendSerializeNameSpace(XmlDocument doc)
            {
                if (string.IsNullOrWhiteSpace(doc.InnerText)) return;
                if (!doc.DocumentElement.HasAttribute("xmlns:xsi"))
                    doc.DocumentElement.SetAttribute("xmlns:xsi", "http://www.w3.org/2001/XMLSchema-instance");
                if (!doc.DocumentElement.HasAttribute("xmlns:xsd"))
                    doc.DocumentElement.SetAttribute("xmlns:xsd", "http://www.w3.org/2001/XMLSchema");
            }

            public static void SerializeToFile(string filePath, T obj, string rootName = null)
            {
                using (StreamWriter sw = new StreamWriter(filePath))
                {
                    XmlSerializer serializer = string.IsNullOrWhiteSpace(rootName) ?
                        new XmlSerializer(typeof(T))
                        : new XmlSerializer(typeof(T), new XmlRootAttribute(rootName));
                    serializer.Serialize(sw, obj);
                }
            }

            public static T DeserializeFromFile(string filePath)
            {
                using (StreamReader sr = new StreamReader(filePath))
                {
                    XmlSerializer serializer = new XmlSerializer(typeof(T));
                    return (T)serializer.Deserialize(sr);
                }
            }

            public static T Deserialize(string xmlString)
            {
                T cloneObject = default(T);

                StringBuilder buffer = new StringBuilder();
                buffer.Append(xmlString);

                XmlSerializer serializer = new XmlSerializer(typeof(T));

                using (TextReader reader = new StringReader(buffer.ToString()))
                {
                    Object obj = serializer.Deserialize(reader);
                    cloneObject = (T)obj;
                }

                return cloneObject;
            }

        }