How to Edit MS Word Text with C# Console Application

using System.Runtime.InteropServices;
using Microsoft.Office.Interop.Word;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            const string documentLocation = @"C:\Users\chmosama\Desktop\Demo.docx"; //<-- File Location you want to edit
            const string findText1 = "<firstname>"; //<-- The text you want to edit
            const string replaceText1 = "Ch M"; //<-- The text you want to replace

            const string findText2 = "<lastname>"; //<-- The text you want to edit
            const string replaceText2 = "Osama"; //<-- The text you want to replace

            FindReplace(documentLocation, findText1, replaceText1);
            FindReplace(documentLocation, findText2, replaceText2);
        }

        private static void FindReplace(string documentLocation, string findText, string replaceText)
        {
            var app = new Application();
            var doc = app.Documents.Open(documentLocation);
            var range = doc.Range();
            range.Find.Execute(FindText: findText, Replace: WdReplace.wdReplaceAll, ReplaceWith: replaceText);
            var shapes = doc.Shapes;
            foreach (Shape shape in shapes)
            {
                var initialText = shape.TextFrame.TextRange.Text;
                var resultingText = initialText.Replace(findText, replaceText);
                shape.TextFrame.TextRange.Text = resultingText;
            }
            doc.Save();
            doc.Close();
            Marshal.ReleaseComObject(app);
        }
    }
}