Linq入门演练---(1)基本用法-分组，排序,内连接

这一节大家共同学习下LINQ的基本用法，主要包括LINQ的分组，排序，和内外连接。

1.分组

基本语法: group element by key

element 表示查询结果返回的元素，key表示分组条件。group子句返回的类型为IGrouping<TKey,TElement>的查询结果。

IGrouping<TKey,TElement>可以看成一个hashtable内部嵌套一个list列表的数据结果. 其中TElement就是一个list

我们看下面的一个事例，下面这个实例演示根据性别对用户进行分组

代码

[csharp]
public class User
    {
        public User(string userName,string sex,int age)
        {
            UserName = userName;
            Sex = sex;
            Age = age;
        }

        public string UserName
        {
            get;
            set;
        }

        public string Sex
        {
            get;
            set;
        }

        public int Age
        {
            get;
            set;
        }
    }
public class User
    {
        public User(string userName,string sex,int age)
        {
            UserName = userName;
            Sex = sex;
            Age = age;
        }

        public string UserName
        {
            get;
            set;
        }

        public string Sex
        {
            get;
            set;
        }

        public int Age
        {
            get;
            set;
        }
    }

[csharp]
private void button1_Click(object sender, EventArgs e)
        {
            User[] users = {
                           new User("刘德华","男",40),
                           new User("张学友","男",30),
                           new User("张曼玉","女",35),
                           new User("杨幂","女",53)
                           };

            var query1 =
                  from var1 in users
                  group var1 by var1.Sex;

            string str = "";
            foreach (var item in query1)
            {
                str += item.Key + "\r\n";

                foreach (var user in item)
                {
                    str += user.UserName + "--" + user.Sex + "--" + user.Age.ToString() + "\r\n";
                }

            }
            textBox1.Text = str;

        }
private void button1_Click(object sender, EventArgs e)
        {
            User[] users = {
                           new User("刘德华","男",40),
                           new User("张学友","男",30),
                           new User("张曼玉","女",35),
                  &

补充：软件开发 , C# ,