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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 易做图,int age) 
        { 
            UserName = userName; 
            Sex = 易做图; 
            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 易做图,int age)
        {
            UserName = userName;
            Sex = 易做图;
            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# ,
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