C# XML Linq，读取XML返回NullReferenceException

using System;
using System.Xml.Linq;

class Program
{
    static void Main()
    {
        try
        {
            XDocument doc = XDocument.Load("example.xml");
            XElement root = doc.Root;

            // 检查根节点是否为空
            if (root != null)
            {
                XElement element = root.Element("SomeElement");

                // 检查指定节点是否存在
                if (element != null)
                {
                    string value = element.Value;
                    Console.WriteLine(value);
                }
                else
                {
                    Console.WriteLine("指定节点不存在");
                }
            }
            else
            {
                Console.WriteLine("XML文档为空");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("读取XML时发生异常：" + ex.Message);
        }
    }
}