/// <summary>
        /// 获取已安装的所有NET版本
        /// </summary>
        /// <returns></returns>
        public static List<string> GetDotNetVersions()
        {
            var filepath =Environment.SystemDirectory + @"\..\Microsoft.NET\Framework";
            DirectoryInfo[] directories = new DirectoryInfo(filepath).GetDirectories("v?.?.*");
            List<string> list = new List<string>();
            foreach (DirectoryInfo info in directories)
            {
                list.Add(info.Name.Substring(1));
            }
            return list;
        }