Question

我有多个班级列表。

public class MainClass
{
 public List<A> a{ get; set; }
 public List<B> b{ get; set; }
 public List<C> c{ get; set; }
}

主要类包含以下属性

 class A
    {
      public string Name{ get; set; }
      public string MainAddress{get;set;}
    }

    class B
    {
      public int ID {get;set;}
      public string Address{ get; set; }
    }

    class C
    {
     public int ID {get;set;}
      public string Name{ get; set; }
    }

现在我如何从列表b＆amp;获取数据？ c 并将其传递给 A 这是我试过的

  List<A> query = (from b in MainClass.b
               join c in Mainclass.c
                on b.ID equals c.ID
                select new {b.Address, c.Name});

如何在C中将名称显示为A

中的主要地址

Answer 1

如果我错了，请纠正我，但我认为你想要的是A列表中有来自c列表的MainAddresses。如果是这样的话：

 var query = (from b in MainClass.b
               join c in Mainclass.c
                on b.ID equals c.ID
                select new A { MainAddress = c.Name });

修改：我继续做了一个完整的工作示例，以便你可以检查你的错误......

A，B和C类必须具有与a，b和c属性相同的可见性。

您正在静态访问b和c，但它们是实例变量。

当然，通过直接在Enumerable实例上调用ToList选择器，可以一步完成从Enumerable到List的转换。

namespace ConsoleApplication1 { class Program { static void Main(string[] args) { var mainClass = new MainClass(); mainClass.b = new List<B>(); mainClass.c = new List<C>(); mainClass.b.Add(new B { ID = 1, Address = "B1" }); mainClass.c.Add(new C { ID = 1, Name = "C1" }); //using LINQ var query = (from b in mainClass.b join c in mainClass.c on b.ID equals c.ID select new A { MainAddress = c.Name }); List<A> fromLINQ = query.ToList(); //using anonymous functions aka lambda expressions IEnumerable<A> enumerableFromAnonymous = mainClass.b.Join(mainClass.c, x => x.ID, x => x.ID, (x, y) => { return new A() { MainAddress = y.Name }; }); List<A> listFromAnonymous = enumerableFromAnonymous.ToList(); } } public class MainClass { public List<A> a { get; set; } public List<B> b { get; set; } public List<C> c { get; set; } } public class A { public string Name { get; set; } public string MainAddress { get; set; } } public class B { public int ID { get; set; } public string Address { get; set; } } public class C { public int ID { get; set; } public string Name { get; set; } } }

Answer 2

下面是演示代码的完整代码段：http://share.linqpad.net/aq8f6c.linq

要将B中的地址显示为A中的Mainadress，请执行以下操作：

var result = from a in As
             join b in (from b in Bs
                        join c in Cs
                        on b.ID equals c.ID
                        select new {b.Address, c.Name})
             on a.Name equals b.Name
             select new A {
                 Name = a.Name,
                 MainAddress = b.Address
             };

result则为Ienumerable<A>类型。

输出：

enter image description here

Answer 3

我认为Serv的例子是正确的答案，但我不喜欢查询语法，因为我发现由于Visual Studio无法在即时窗口中支持Lambda表达式而难以阅读和维护 - 自VS2013起。

我更喜欢使用中间变量的方法语法。这节省了屏幕空间，我认为它更容易理解：

   var query = from a in As
                join c in (from b in Bs
                           join c in Cs
                           on b.ID equals c.ID
                           select new {b.Address, c.Name})
                on a.Name equals c.Name
                select new A {
                    Name = a.Name,
                    MainAddress = c.Address
                };
    query.Dump();

    //method sytnax
    var nameAddress = Bs.Join(Cs, b => b.ID, c => c.ID, (b, c) => new { Name = c.Name, Address = b.Address });
    var query2 = As.Join(nameAddress, a => a.Name, na => na.Name, (a, na) => new { Name = a.Name, MainAddress = na.Address});
    query2.Dump();

使用LINQ从多个列表中选择

3 个答案: