XML Data Lost On System Crash

 
 static Mutex mutex;
 
 public static void AssignObjects()
        {
            if (mutex == null) { mutex = new Mutex(); }
        }
        public static string Get_ValueOfVariable(string VariableName,string Filename)
        {
            AssignObjects();
            mutex.WaitOne();
 
            string ValueIs = "";
            try
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(XMLFileCheck.XMLDirectory + "\\" + Filename);
                string path = "Settings/Vars[Name='" + VariableName.Trim() + "']";
                XmlNode node = doc.SelectSingleNode(path);
                if (node != null)
                {
                    ValueIs = node.LastChild.InnerText;
                }
                else
                {
                    ValueIs = "";
                }
            }
            catch (Exception )
            {
                XMLFileCheck.CheckFor_CorruptedFile(new System.IO.FileInfo(Filename).Name);
            }
            mutex.ReleaseMutex();
            return ValueIs.Trim();
        }

public static string InsertValue_OnVariable(string VariableName, string 
 
Value,string Filename)
        {
            AssignObjects();
            mutex.WaitOne();
 
            string Result = "";
            try
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(XMLFileCheck.XMLDirectory+"\\"+Filename);
 
                string path = "Settings/Vars[Name='" + VariableName.Trim() + "']";
                XmlNode node = doc.SelectSingleNode(path);
                node.LastChild.InnerText = Value.Trim();
 
                doc.Save(XMLFileCheck.XMLDirectory + "\\" + Filename);
               
            }
            catch (Exception)
            {
                XMLFileCheck.CheckFor_CorruptedFile(new System.IO.FileInfo(Filename).Name);
            }
 
            mutex.ReleaseMutex();
            return Result;
        }