Create dropdown form field

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
using Word = Microsoft.Office.Interop.Word;
using Office = Microsoft.Office.Core;
using Microsoft.Office.Tools.Word;

namespace VSTO
{
    public partial class ThisAddIn
    {
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
            //Open document
            Microsoft.Office.Interop.Word.Application wordApp = Application;
            wordApp.Documents.Open("../../Blank.docx");

            //Add a new paragraph
            Word.Paragraph para = this.Application.ActiveDocument.Paragraphs.Add();

            //Get the range of the paragraph
            Word.Range range = para.Range;

            //Add drapdown field
            Word.FormField drop = range.FormFields.Add(range, Word.WdFieldType.wdFieldFormDropDown);
            drop.Name = "DropDownList";
            Word.ListEntries item = drop.DropDown.ListEntries;

            //Add items
            item.Add("one");
            item.Add("Two");
            item.Add("Three");

            //Save the file
            this.Application.ActiveDocument.Save();
        }

        private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
        {
        }

        #region VSTO generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InternalStartup()
        {
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
            this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
        }
        
        #endregion
    }
}