using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace WindowsFormsApp1
{
    public class XpathUpd
    {
        public void testXpathModifying()
        {
            // text xml
            var xml = @"<Data >
    <Inputs>
    <a:ImageInput>
        <a:Name>BSE</a:Name>
    </a:ImageInput>
    </Inputs>
     </Data>";

            XmlDocument xmld = new XmlDocument();

            XmlNamespaceManager nsmgr; // this will hold our namespaces with their prefixes
            xmld.Load(GetReader(xml, out nsmgr)); // xml can also be your file

            // we are going to find a text node, hence cast to XmlText
            var name2 = (XmlText)xmld.SelectSingleNode(
                    "/Data/Inputs/a:ImageInput/a:Name[.='BSE']/text()",
                    nsmgr); // here is the namespace manager so it knows what a is
            if (name2 != null)
            {
                //name2.SetAttribute("a:Name", "{{16}}");
                name2.Value = "{{16}}";
            }

            string AmmendedFile = @"C:\ProgramData\Oxford Instruments NanoAnalysis\XXXX NewXMLReader\Xpath_Mics_Sim.xml";
            xmld.Save(AmmendedFile);
        }

        // Creates a reader and outputs a namespacemanager that fits for the missing namespace prefixes
        XmlReader GetReader(string xml, out XmlNamespaceManager nsmgr)
        {
            // code example taken from
            // https://blogs.msdn.microsoft.com/runeetv/2009/02/12/undeclared-namespace-in-xml-eg-xsi-is-an-undeclared-namespace/
            // from author runeetv and https://blogs.msdn.microsoft.com/runeetv/author/runeetvashisht/

            NameTable nt = new NameTable();
            // add missing namespace prefixes
            nsmgr = new XmlNamespaceManager(nt);
            nsmgr.AddNamespace("a", "urn:why-was-this-left-out?");

            XmlParserContext context = new XmlParserContext(null, nsmgr, null, XmlSpace.None);
            XmlReaderSettings xset = new XmlReaderSettings();
            xset.ConformanceLevel = ConformanceLevel.Fragment;

            // return XmlReader.Create(xml, xset, context); // use this if you want xml to be a filepath
            return XmlReader.Create(new StringReader(xml), xset, context);
        }

    }
}