Выполнение нескольких объединений в операторе LINQ

Question

Может ли кто-нибудь помочь мне перевести следующий SQL-запрос в формат 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' 

Большое спасибо

Answer 1

Я думаю, что это будет что-то вроде:

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); 

     } 

    } 
}