Create XML element with attributes C#

Following is my requirement. I am reading an xml file (*.csproj file) and searching for a node in it. After I find the node I will insert my element into it. Following is my original XML:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://ift.tt/PiGwmX">
    <ItemGroup>
    <ClInclude Include="Stdafx.h" />
    <ClInclude Include="NewFile.h" />
  </ItemGroup>
</Project>

Following is my code snippet to do this.

        XmlDocument xDoc = new XmlDocument();
        xDoc.Load(inputFile);

        XmlNamespaceManager nsMgr = new XmlNamespaceManager(xDoc.NameTable);
        string strNamespace = xDoc.DocumentElement.NamespaceURI;
        nsMgr.AddNamespace("ns", strNamespace);
        XmlNode root = xDoc.SelectSingleNode("/ns:Project/ns:ItemGroup/ns:ClInclude", nsMgr);

        XmlAttribute attr = xDoc.CreateAttribute("Include");
        attr.Value = "NewHeaderFile.h";

        XmlElement xele = xDoc.CreateElement("ClInclude");
        xele.Attributes.Append(attr);

        root.ParentNode.AppendChild(xele);
        xDoc.Save(outFile);

This is the output what i get.

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://ift.tt/PiGwmX">
  <ItemGroup>
    <ClInclude Include="Stdafx.h" />
    <ClInclude Include="NewFile.h" />
    <ClInclude Include="NewHeaderFile.h" xmlns="" />
  </ItemGroup>
</Project>

Problem Statement: I want to ignore the xmlns="" in my output. My output should look like this.

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://ift.tt/PiGwmX">
  <ItemGroup>
    <ClInclude Include="Stdafx.h" />
    <ClInclude Include="NewFile.h" />
    <ClInclude Include="NewHeaderFile.h" />
  </ItemGroup>
</Project>

Kinldy help me. Thanks for your valuable time.