Thực hiện nhiều phép nối trong một câu lệnh LINQ

Question

Ai đó có thể giúp tôi dịch truy vấn SQL sau sang định dạng LINQ.

SELECT a.ID, 
     a.HostID, 
     h.URL, 
     a.SourceURL, 
     a.TargetURL, 
     c.Value, 
     a.ExtFlag 
FROM Link a 
INNER JOIN Host h 
ON h.ID = a.HostID 
INNER JOIN Ref c 
ON a.ResponseCode = c.SubType 
AND c.Type = 'HTTP Status' 

Nhiều Cảm ơn

Answer 1

Tôi nghĩ rằng nó sẽ là một cái gì đó như:

var result = from a in Context.DGApprovedLink 
      join h in Context.DGHost on a.HostID equals h.ID 
      join c in Context.DGConfig on a.ResponseCode equals c.SubType 
      where c.Type == "HTTP Status" 
      select new { 
       a.ID, 
       a.HostID, 
       h.URL, 
       a.SourceURL, 
       a.TargetURL, 
       c.Value, 
       a.ExtFlag }; 

Answer 2

Create Unit test class using MStest and copy the code 

using System; 
using System.Collections.Generic; 
using System.Linq; 
using Microsoft.VisualStudio.TestTools.UnitTesting; 

namespace LinqTest.Test 
{ 

    public class Employee 
    { 
     public int EmpId { get; set; } 
     public string Name { get; set; } 
     public DateTime? DOB { get; set; } 
     public decimal Salary { get; set; } 
     public DateTime DOJ { get; set; } 
     public bool IsActive { get; set; } 
    } 


    public class Book 
    { 
     public int BookId { get; set; } 
     public string Title { get; set; } 
     public double Price { get; set; } 
    } 

    public class BookOrder 
    { 
     public int OrderId { get; set; } 
     public int EmpId { get; set; } 
     public int BookId { get; set; } 
     public int Quantity { get; set; } 
    } 



    [TestClass] 
    public class Linqtest 
    { 
     List<Employee> Employees; 
     List<Book> Books; 
     List<BookOrder> Orders; 

     [TestInitialize] 
     public void InitializeData() 
     { 
      Employees = new List<Employee>(); 
      Books = new List<Book>(); 
      Orders = new List<BookOrder>(); 

      Employees.Add(new Employee(){EmpId = 1, Name ="Test1" , DOB = new DateTime(1980,12,15),IsActive = true,Salary = 4500}); 
      Employees.Add(new Employee() { EmpId = 11, Name = "Test2", DOB = new DateTime(1981, 12, 15), IsActive = true, Salary = 3500 }); 
      Employees.Add(new Employee() { EmpId = 5, Name = "Test3", DOB = new DateTime(1970, 2, 15), IsActive = true, Salary = 5500 }); 
      Employees.Add(new Employee() { EmpId = 8, Name = "Test4", DOB = new DateTime(1978, 1, 15), IsActive = true, Salary = 7500 }); 
      Employees.Add(new Employee() { EmpId = 9, Name = "Test5", DOB = new DateTime(1972, 2, 5), IsActive = true, Salary = 2500 }); 
      Employees.Add(new Employee() { EmpId = 10, Name = "Test6", DOB = new DateTime(1980, 10, 8), IsActive = false, Salary = 5500 }); 
      Employees.Add(new Employee() { EmpId = 15, Name = "Test7", DOB = new DateTime(1983, 11, 25), IsActive = true, Salary = 3500 }); 

      Books.Add(new Book(){BookId = 2, Price = 24.99,Title = "British Food"}); 
      Books.Add(new Book() { BookId = 5, Price = 4.99, Title = "Holidays in UK" }); 
      Books.Add(new Book() { BookId = 7, Price = 7.99, Title = "UK Laws" }); 


      Orders.Add(new BookOrder(){EmpId = 1,OrderId = 1,BookId = 2,Quantity = 3}); 
      Orders.Add(new BookOrder() { EmpId = 1, OrderId = 1, BookId = 5, Quantity = 1 }); 
      Orders.Add(new BookOrder() { EmpId = 1, OrderId = 2, BookId = 7, Quantity = 5 }); 
      Orders.Add(new BookOrder() { EmpId = 11, OrderId = 3, BookId = 2, Quantity = 3 }); 
      Orders.Add(new BookOrder() { EmpId = 11, OrderId = 4, BookId = 7, Quantity = 3 }); 
     } 


     [TestMethod] 
     public void CheckEmpCount() 
     { 

      var res = Employees 
       .Where(e => e.EmpId > 5) 
       .Where(t =>t.Salary>=5000); 

      Assert.AreEqual(2,res.Count()); 

      res = Employees 
       .Where(e => e.EmpId > 5); 

      Assert.AreEqual(5,res.Count()); 

     } 

     [TestMethod] 
     public void TestGroupBy() 
     { 
      var res = from e in Employees 
       group e by e.Salary; 

      Assert.AreEqual(5,res.Count()); 

      var res1 = Employees.GroupBy(e => e.Salary); 
      Assert.AreEqual(5, res1.Count()); 
     } 

     [TestMethod] 
     public void TestJoin() 
     { 
      var res = from o in Orders 
       join Employee e in Employees 
        on o.EmpId equals e.EmpId 
       where o.EmpId == 11 
       select o; 

      Assert.AreEqual(2,res.Count()); 
     } 

     [TestMethod] 
     public void TestJoinData() 
     { 
      var res = from o in Orders 
       join Employee e in Employees 
        on o.EmpId equals e.EmpId 
       join Book b in Books 
        on o.BookId equals b.BookId 
       orderby e.EmpId 
       select new {o.OrderId, e.Name, b.Title, b.Price}; 

      Assert.AreEqual("Test1", res.First().Name); 

     } 

    } 
}