译文出处:
今天在这个话题中,我给大家分享一个在c#编程中非常有趣和十分有用的特性。
开始之前,我想告诉大家关于Linq的基本信息。比如:什么是linq?然后再来分享实际应用。
说明:
LINQ = Language Integrated Query(集成查询语言)
Linq是微软在.NET Framework 3.5中信增加的一个特性。它是用来查询数据库和对数据库查询的本地集合带来安全性。它非常简单但是很有组织性。一个普通的查询语言,适用于SQL, XML, 本地collections 和 第三方APIs 比如SharePoint.
本质上,Linq提供的就是一个轻量级的编程数据集成。这是非常有价值的,尤其是当今每天面对的数据和未来的大数据。
接下来我们就看看这个神秘的东东。
第一步:
- 打开你的Visual Studio 并且创建一个新的控制台项目.
- 然后打开服务器资源管理,创建一个新的数据库,新增一张表增加几个字段。
- 打开你的项目的解决方案目录,右击工程点击添加新增项。
- 查找LINQ-To-SQL 并添加。
- 你会看到一个空白的文件,在这个文件中你可以拖动你的表放在 LINQ-To-SQL .dbml 文件扩展上.
第二步:
我将声明一些类,添加一些类成员。
1 class Program2 { // this is program class3 private int id;4 private string name;5 private string fname;6 private int age;7 private string sem;8 }
第三步:
这里我将告诉大家如何通过 LINQ-To-SQL 向数据库中插入数据。
1 public void insert() 2 { 3 // these are the class data members through we will send our objects data in the database 4 Console.WriteLine("Enter id"); 5 id = Convert.ToInt32(Console.ReadLine()); 6 Console.WriteLine("Enter name"); 7 name = Console.ReadLine(); 8 Console.WriteLine("Enter father name"); 9 fname = Console.ReadLine();10 Console.WriteLine("Enter age");11 age = Convert.ToInt32(Console.ReadLine());12 Console.WriteLine("Enter semester");13 sem = Console.ReadLine();14 // this is the data context class the main class which handles 15 // all the functionality in this will pass the connection string of our database file.16 LTSDataContext LTS = new LTSDataContext17 (@"Data Source=(LocalDB)\v11.0;18 AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\19 ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;20 Integrated Security=True;Connect Timeout=30");21 // this is the table class which we drag on our linq to sql file22 Student objStudentTable = new Student();23 objStudentTable.Id = id;24 objStudentTable.Name = name;25 objStudentTable.Father_Name = fname;26 objStudentTable.Age = age;27 objStudentTable.Semester = sem;28 LTS.Students.InsertOnSubmit(objStudentTable); // this is built in function.29 LTS.SubmitChanges();// here is the final query will run in the data context class.30 }
第四步:展示数据
1 void Display() 2 { 3 LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0; 4 AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\ 5 ConsoleApplication5\ConsoleApplication5\SDatabase.mdf; 6 Integrated Security=True;Connect Timeout=30"); 7 var selectQuery = from s in LTS.Students 8 select s; 9 foreach (Student s in selectQuery)10 {11 Console.WriteLine(s.Id + "\t" + s.Name + "\t" + 12 s.Father_Name + "\t" + s.Age + "\t" + s.Semester);13 }14 }
第五步:删除数据
1 void Delete() 2 { 3 int iid = 0; 4 Console.WriteLine("Enter the Id of the student u want to delete?"); 5 iid = Convert.ToInt32(Console.ReadLine()); 6 7 LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0; 8 AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\ 9 ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;10 Integrated Security=True;Connect Timeout=30");11 var delete = from p in LTS.Students12 where p.Id == iid13 select p;14 LTS.Students.DeleteAllOnSubmit(delete);15 LTS.SubmitChanges();16 Student objStudentTable = LTS.Students.Single(c=> c.Id == iid); 17 }
第六步:更新数据
1 void update() 2 { 3 LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0; 4 AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\ 5 ConsoleApplication5\ConsoleApplication5\SDatabase.mdf; 6 Integrated Security=True;Connect Timeout=30"); 7 Student objStudentTable = new Student(); 8 int iid = 0; 9 Console.WriteLine("Enter the Id of the student u want to update ?");10 iid = Convert.ToInt32(Console.ReadLine());11 12 Console.WriteLine("Enter the new name of the student u want to update?");13 string up = (Console.ReadLine());14 var update = from s1 in LTS.Students15 where s1.Id == iid16 select s1;17 foreach (var v in update)18 v.Name = up;19 LTS.SubmitChanges();20 }
主函数:
1 static void Main(string[] arg){2 3 Program p1 = new Program(); // creates object 4 p1.insert();5 p1.Display();6 p1.Delete();7 p1.update();8 Console.ReadKey();9 }
感谢您的阅读,请留下您的足迹。
Cheers! Enjoy coding.