小编Man*_*dan的帖子

我试图安装离子并从早上开始创建一个示例项目.但是,从那时起就面临着一系列问题.试图一个一个地解决它们.Atlast重新启动我的机器并打开命令提示符来构建示例项目并尝试

path of the sample project> ionic build android

但是,我继续面对错误,即'离子'未被认为是内部或外部命令.

我尝试清除缓存并在我的机器中重新安装离子.尽管如此,我面临同样的离子问题并未被认为是内部或外部的命令.

有人可以帮我解决这个问题吗？

谢谢Manikandan J.

实际上,我正在尝试按城市分组学生名单.当我执行此操作时,我在s2.City附近的LINQ语句中出现"对象引用"错误.

class Groupby
    {
        Student[] s = new Student[10];

        public Groupby()
        {
            s[0] = new Student("Manikandan", "Jayagopi", "Chennai");

            s[1] = new Student("Ganesh", "Bayyanna", "Bangalore");

            s[2] = new Student("Laxman", "Bharghav", "Hyderabad");

            s[3] = new Student("Dinesh","Vellaiyan","Pune");

            s[4] = new Student("Natarajan","Nallathambi","Chennai");
        }

        public void Group()
        {                
            var groupQuery = from s2 in s
                             group s2 by s2.City;

            foreach (Student s1 in groupQuery)
                Console.WriteLine(" {0}", s1.FirstName);

        }
    }

class Program
    {
static void Main()
        {            
            Groupby objGroupby = new Groupby();

            objGroupby.Group();

            Console.ReadLine();
        }
    } …