how do I link the class with main method in the same file

This is my first time using C# to create the program. How do I GetXMLData then add the record after that update the data in xml file? This program do not return me the error, but I could not see the data id "4" has been added into the record.

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


namespace LinQ
{
    class Program
    {

        private string path = "TestData.xml";

        private void GetXMLData()
        {
           // try
           // {
                XDocument testXML = XDocument.Load(path);
                var students = from student in testXML.Descendants("Student")
                               select new
                               {
                                   ID = Convert.ToInt32(student.Attribute("ID").Value),
                                   Name = student.Element("Name").Value
                               };

                foreach (var student in students)
                {
                    // Do other operations with each student object

                }
          //  }
            //catch (Exception err)
            //{
            //    MessageBox.Show(err.Message);
            //}
        }
        private void InsertXMLData(string name)
        {
            //try
            //{
                XDocument testXML = XDocument.Load(path);

                XElement newStudent = new XElement("Student",
                                               new XElement("Name", name)
                                           );
                var lastStudent = testXML.Descendants("Student").Last();

                int newID = Convert.ToInt32(lastStudent.Attribute("ID").Value);
                newStudent.SetAttributeValue("ID", 4);
                testXML.Element("Students").Add(newStudent);
                testXML.Save(path);
            //}
            //catch (Exception err)
            //{
            //    MessageBox.Show(err.Message);
            //}
        }

        private void UpdateXMLData(string name, int id)
        {
            //try
            //{
                XDocument testXML = XDocument.Load(path);
                XElement cStudent = testXML.Descendants("Student").Where(c => c.Attribute("ID").Value.Equals(id.ToString())).FirstOrDefault();

                cStudent.Element("Name").Value = name;
                testXML.Save(path);
            //}
            //catch (Exception err)
            //{
            //    MessageBox.Show(err.Message);
            //}
        }

        static void Main(string[] args)
        {
            //GetXMLData();
            //InsertXMLData(string name);


        }

    }
}