Xml file write not working in repository level in MVC

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C#

XML

MVC4

My project structure is like below
1. ApplicationUI is one project
2. Service is another library project
3. Repository is db level library project

and i have added the xml file in Repository level like below
Repository/XMLUserDetails.xml

when i tried to insert the data by using the below code then i am getting the error like this "

Could not find a part of the path

"

Not able to insert the data into xml whne i have maintained xml in Repository level.

What I have tried:

string xmlFileName = "~\\XMLUserDatabase.xml";
                XmlDocument oXmlDocument = new XmlDocument();
                oXmlDocument.Load(HttpContext.Current.Server.MapPath(xmlFileName));
                XmlNodeList nodelist = oXmlDocument.GetElementsByTagName("UsrDetails");
                XDocument xmlDoc = XDocument.Load(HttpContext.Current.Server.MapPath(xmlFileName));
                xmlDoc.Element("UsrDetails")
                    .Add(   new XElement("EmailAddress", objUserDetailsRequest.EmailAddress), 
                            new XElement("Password", objUserDetailsRequest.Password));
                xmlDoc.Save(HttpContext.Current.Server.MapPath(xmlFileName));

System.Xml.XmlDocument myXml = new System.Xml.XmlDocument();
                myXml.Load(System.Web.Hosting.HostingEnvironment.MapPath("~/XMLUserDetails.xml"));
                System.Xml.XmlNode xmlNode = myXml.DocumentElement.FirstChild;
                System.Xml.XmlElement xmlElement = myXml.CreateElement("UserDetails");

                xmlElement.SetAttribute("EmailAddress", objUserDetailsRequest.EmailAddress);
                xmlElement.SetAttribute("Password", objUserDetailsRequest.Password);
               

                myXml.DocumentElement.InsertBefore(xmlElement, xmlNode);
                myXml.Save(System.Web.Hosting.HostingEnvironment.MapPath("~/XMLUserDetails.xml"));

                 XmlTextReader xmlReader = new XmlTextReader(System.Web.Hosting.HostingEnvironment.MapPath("~/XMLUserDetails.xml"));
        xmlReader.Close();