譯：在C#中使用LINQ To SQL

譯文出處：http://www.codeproject.com/Tips/871938/LINQ-To-SQL-Using-Csharp

 今天在這個話題中，我給大家分享一個在c#編程中非常有趣和十分有用的特性。

開始之前，我想告訴大家關於Linq的基本信息。比如：什么是linq？然后再來分享實際應用。

說明：

LINQ = Language Integrated Query（集成查詢語言）

Linq是微軟在.NET Framework 3.5中信增加的一個特性。它是用來查詢數據庫和對數據庫查詢的本地集合帶來安全性。它非常簡單但是很有組織性。一個普通的查詢語言，適用於SQL, XML, 本地collections 和 第三方APIs 比如SharePoint.

本質上，Linq提供的就是一個輕量級的編程數據集成。這是非常有價值的，尤其是當今每天面對的數據和未來的大數據。

接下來我們就看看這個神秘的東東。

第一步：

 

• 打開你的Visual Studio 並且創建一個新的控制台項目.
• 然后打開服務器資源管理，創建一個新的數據庫，新增一張表增加幾個字段。
• 打開你的項目的解決方案目錄，右擊工程點擊添加新增項。
• 查找LINQ-To-SQL 並添加。
• 你會看到一個空白的文件,在這個文件中你可以拖動你的表放在 LINQ-To-SQL .dbml 文件擴展上.

第二步：

我將聲明一些類，添加一些類成員。

class Program
    {                            // this is  program class
        private int id;
        private string name;
        private string fname;
        private int age;
        private string sem;
}

第三步：

這里我將告訴大家如何通過 LINQ-To-SQL 向數據庫中插入數據。

public void insert()
        {
// these are the class data members through we will send our objects data in the database
            Console.WriteLine("Enter id");
            id = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Enter name");
            name = Console.ReadLine();
            Console.WriteLine("Enter father name");
            fname = Console.ReadLine();
            Console.WriteLine("Enter age");
            age = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Enter semester");
            sem = Console.ReadLine();
// this is the data context class the main class which handles 
// all the functionality in this will pass the connection string of our database file.
            LTSDataContext LTS = new LTSDataContext
            (@"Data Source=(LocalDB)\v11.0;
            AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\
            ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;
        Integrated Security=True;Connect Timeout=30");
        // this is the table class which we drag on our linq to sql file
            Student objStudentTable = new Student();
            objStudentTable.Id = id;
            objStudentTable.Name = name;
            objStudentTable.Father_Name = fname;
            objStudentTable.Age = age;
            objStudentTable.Semester = sem;
            LTS.Students.InsertOnSubmit(objStudentTable); // this is built in function.
            LTS.SubmitChanges();// here is the final query will run in the data context class.
        }

第四步：展示數據

 

void Display()
        {
            LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0;
            AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\
            ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;
        Integrated Security=True;Connect Timeout=30");
            var selectQuery = from s in LTS.Students
                              select s;
            foreach (Student s in selectQuery)
            {
                Console.WriteLine(s.Id + "\t" + s.Name + "\t" + 
        s.Father_Name + "\t" + s.Age + "\t" + s.Semester);
            }
        }

第五步：刪除數據

 

void Delete()
        {
            int iid = 0;
            Console.WriteLine("Enter the Id of the student u want to delete?");
            iid = Convert.ToInt32(Console.ReadLine());

            LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0;
            AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\
            ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;
        Integrated Security=True;Connect Timeout=30");
            var delete = from p in LTS.Students
                         where p.Id == iid
                         select p;
            LTS.Students.DeleteAllOnSubmit(delete);
            LTS.SubmitChanges();
            Student objStudentTable = LTS.Students.Single(c=> c.Id == iid);    
        }

第六步：更新數據

 

void update()
        {
            LTSDataContext LTS = new LTSDataContext(@"Data Source=(LocalDB)\v11.0;
            AttachDbFilename=C:\Users\Ehtesham Mehmood\Documents\Visual Studio 2012\Projects\
            ConsoleApplication5\ConsoleApplication5\SDatabase.mdf;
        Integrated Security=True;Connect Timeout=30");
            Student objStudentTable = new Student();
            int iid = 0;
            Console.WriteLine("Enter the Id of the student u want to update ?");
            iid = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("Enter the new name of the student u want to update?");
            string up = (Console.ReadLine());
                var update = from s1 in LTS.Students
                             where s1.Id == iid
                             select s1;
                foreach (var v in update)
                    v.Name = up;
                LTS.SubmitChanges();
        }

主函數：

 

static void Main(string[] arg){
            
           Program p1 = new Program();     // creates object 
           p1.insert();
           p1.Display();
           p1.Delete();
           p1.update();
            Console.ReadKey();
        }

感謝您的閱讀，請留下您的足跡。

Cheers! Enjoy coding.