Create a new Microsoft Word document add two content controls with the names:

• Employee_Firstname
• Employee_Lastname

Like:

Employee_Lastname

Now when you run the unittest below, the following the result will be:

namespace EndToEndTest
{
    using DocumentFormat.OpenXml;
    using DocumentFormat.OpenXml.CustomXmlDataProperties;
    using DocumentFormat.OpenXml.Packaging;
    using DocumentFormat.OpenXml.Wordprocessing;
    using Microsoft.VisualStudio.TestTools.UnitTesting;
    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;
    using System.Xml;
    using System.Xml.Linq;

    [TestClass]
    public class RliResearch
    {
        private List<string> _tagNames = new List<string>();
        private List<string> _uniqueTagNames = new List<string>();

        [TestMethod]
        public void Test_with_duration()
        {
            var watch = new System.Diagnostics.Stopwatch();
            watch.Start();

            InitialiseDatabinding();

            watch.Stop();
            System.Console.WriteLine(watch.Elapsed.TotalMilliseconds);
        }

        public void InitialiseDatabinding()
        {
            using (WordprocessingDocument doc = WordprocessingDocument.Open(@"C:\Temp\Test.docx", true))
            {
                
                CustomXmlPart customXmlPart = doc.MainDocumentPart.CustomXmlParts.FirstOrDefault();
                if (customXmlPart == null)
                {
                    customXmlPart = doc.MainDocumentPart.AddCustomXmlPart(CustomXmlPartType.CustomXml);
                }

                if (customXmlPart.CustomXmlPropertiesPart == null)
                {
                    customXmlPart.AddNewPart<CustomXmlPropertiesPart>();
                }

                var propertiesPart = customXmlPart.CustomXmlPropertiesPart;

                if(propertiesPart.DataStoreItem == null)
                {
                    var dataStoreItem = new DataStoreItem() { ItemId = Guid.NewGuid().ToString("B") };
                    propertiesPart.DataStoreItem = dataStoreItem;
                }

                string dataStoreId = customXmlPart.CustomXmlPropertiesPart.DataStoreItem.ItemId;

                var names = new List<string>();

                foreach (var cc in doc.ContentControls())
                {
                    SdtProperties props = cc.Elements<SdtProperties>().FirstOrDefault();
                    if (props != null)
                    {
                        string name = string.Empty;
                        try
                        {
                            Tag tag = props.Elements<Tag>().FirstOrDefault();
                            if (tag != null)
                            {
                                name = tag.Val.ToString();
                                names.Add(name);
                                tag.Val = name;

                                DocumentFormat.OpenXml.Wordprocessing.SdtAlias alias = props.Elements<DocumentFormat.OpenXml.Wordprocessing.SdtAlias>().FirstOrDefault();
                                if (alias != null)
                                {
                                    alias.Val = name;
                                }

                                // Update databinding
                                DocumentFormat.OpenXml.Wordprocessing.DataBinding dataBinding = props.Elements<DocumentFormat.OpenXml.Wordprocessing.DataBinding>().FirstOrDefault();
                                if (dataBinding == null)
                                {
                                    dataBinding = new DataBinding();
                                    dataBinding.XPath = string.Format("/Root[1]/{0}[1]", name);
                                    dataBinding.StoreItemId = dataStoreId;
                                    props.Append(dataBinding);
                                }
                                else
                                {
                                    dataBinding.XPath = string.Format("/Root[1]/{0}[1]", name);
                                    dataBinding.StoreItemId = dataStoreId;
                                }
                            }
                        }
                        catch (Exception ex)
                        {
                            throw new ApplicationException(string.Format("Exception found during processing of tag [{0}].", name), ex);
                        }
                    }
                }

                List<string> uniqueTagNames = names.Distinct(StringComparer.CurrentCultureIgnoreCase).OrderBy(x => x).ToList();

                XDocument xdoc = CreateXmlDocument("Root", uniqueTagNames);

                SaveCustomXmlPart(customXmlPart, xdoc);
            }
        }

        /// <summary>
        /// Create a XDocument, with a root element based on the given "rootName", containing child elements based on the given "tagnames".
        /// </summary>
        public XDocument CreateXmlDocument(string rootName, List<string> tagNames)
        {
            var document = new XDocument(
                new XDeclaration("1.0", "utf-8", null),
                    new XElement(rootName,
                        tagNames.Select(x => 
                        {
                            XElement xe = new XElement(x, string.Empty);
                            if(string.Compare(x, "Employee_Firstname", true) == 0)
                            {
                               xe = new XElement(x, "Johny");
                            }
                            if (string.Compare(x, "Employee_Lastname", true) == 0)
                            {
                               xe= new XElement(x, "Droptables");
                            }
                            return xe;
                        }
                    )
                )
            );

            return document;
        }

        public void SaveCustomXmlPart(CustomXmlPart part, XDocument xdoc)
        {
            using (var stream = part.GetStream(FileMode.Create, FileAccess.ReadWrite))
            {
                // Reset stream position to 0, to prevent errors.
                stream.Position = 0;

                using (XmlWriter xw = XmlWriter.Create(stream))
                {
                    xdoc.Save(xw);
                }
            }
        }
    }
   
    /// <summary>
    /// Code from: http://openxmldeveloper.org/blog/b/openxmldeveloper/archive/2011/04/11/137383.aspx
    /// </summary>
    public static class ContentControlExtensions
    {
        public static IEnumerable<OpenXmlElement> ContentControls(
            this OpenXmlPart part)
        {
            return part.RootElement
                .Descendants()
                .Where(e => e is SdtBlock || e is SdtRun);
        }

        public static IEnumerable<OpenXmlElement> ContentControls(
            this WordprocessingDocument doc)
        {
            foreach (var cc in doc.MainDocumentPart.ContentControls())
                yield return cc;
            foreach (var header in doc.MainDocumentPart.HeaderParts)
                foreach (var cc in header.ContentControls())
                    yield return cc;
            foreach (var footer in doc.MainDocumentPart.FooterParts)
                foreach (var cc in footer.ContentControls())
                    yield return cc;
            if (doc.MainDocumentPart.FootnotesPart != null)
                foreach (var cc in doc.MainDocumentPart.FootnotesPart.ContentControls())
                    yield return cc;
            if (doc.MainDocumentPart.EndnotesPart != null)
                foreach (var cc in doc.MainDocumentPart.EndnotesPart.ContentControls())
                    yield return cc;
        }
    }
}