LINQ简单使用与XML的转换

分手后的思念是犯贱 2021-06-24 16:09 357阅读 0赞

# LINQ是什么？ #

LINQ（Language Integrated Query）语言集成查询是一组用于c\#和Visual Basic语言的扩展。它允许编写C\#或者Visual Basic代码以操作内存数据的方式，查询数据库。

# LINQ怎么读？ #

lin-k    在这里Q不发q的音，而是发k的音，所以读做link。

# 使用LINQ进行不同的操作 #

### 查询、筛选并进行排序与分组的操作 ###

var custQuery =
    
        from cust in customers
    
        group cust by cust.City into custGroup
    
        where custGroup.Count() > 2
    
        orderby custGroup.Key
    
        select custGroup;

### 联接操作 ###

var innerJoinQuery =
    
        from cust in customers
    
        join dist in distributors on cust.City equals dist.City
    
        select new { CustomerName = cust.Name, DistributorName = dist.Name };

### 将内存中对象转换为XML ###

class XMLTransform
    
    {
    
        static void Main()
    
        {           
    
            // Create the data source by using a collection initializer.
    
            // The Student class was defined previously in this topic.
    
            List<Student> students = new List<Student>()
    
            {
    
                new Student {First="Svetlana", Last="Omelchenko", ID=111, Scores = new List<int>{97, 92, 81, 60}},
    
                new Student {First="Claire", Last="O’Donnell", ID=112, Scores = new List<int>{75, 84, 91, 39}},
    
                new Student {First="Sven", Last="Mortensen", ID=113, Scores = new List<int>{88, 94, 65, 91}},
    
            };
    
    
    
            // Create the query.
    
            var studentsToXML = new XElement("Root",
    
                from student in students
    
                let x = String.Format("{0},{1},{2},{3}", student.Scores[0],
    
                        student.Scores[1], student.Scores[2], student.Scores[3])
    
                select new XElement("student",
    
                           new XElement("First", student.First),
    
                           new XElement("Last", student.Last),
    
                           new XElement("Scores", x)
    
                        ) // end "student"
    
                    ); // end "Root"
    
    
    
            // Execute the query.
    
            Console.WriteLine(studentsToXML);
    
    
    
            // Keep the console open in debug mode.
    
            Console.WriteLine("Press any key to exit.");
    
            Console.ReadKey();
    
        }
    
    }

然后生成的xml文件如下：

<Root> 
    
      <student> 
    
        <First>Svetlana</First> 
    
        <Last>Omelchenko</Last> 
    
        <Scores>97,92,81,60</Scores> 
    
      </student> 
    
      <student> 
    
        <First>Claire</First> 
    
        <Last>O'Donnell</Last> 
    
        <Scores>75,84,91,39</Scores> 
    
      </student> 
    
      <student> 
    
        <First>Sven</First> 
    
        <Last>Mortensen</Last> 
    
        <Scores>88,94,65,91</Scores> 
    
      </student> 
    
    </Root>