在LINQ语句中执行多个连接

有人可以帮助我将以下SQL查询转换为LINQ格式。

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' 

非常感谢

Answer 1

我认为它会是这样的：

 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 Employees; List Books; List Orders; [TestInitialize] public void InitializeData() { Employees = new List(); Books = new List(); Orders = new List(); 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); } } }