如何比较基于常见字符串值的两个列表？

问题描述：

list1{ 
     new Object1{ State= "AL" , Value = 3.123} 
     new Object2{ State= "CO", Value = 2.111} 
     } 

list2{ 
     new Object1{State="AL", Value=2.123} 
     new Object2{State="CO", Value=3.111} 
    }

我需要比较这两个列表，并产生另一个列表如下所示：

list3{ 
     new Object1{State="AL", Value= (3.123 + 2.123)} 
     new Object2{ State="CO", Value =(2.111 + 3.111) } 
    }

有人可以告诉我，我该怎么做这个？

我不是LINQ专家，但是你的代码示例似乎不是有效的C＃语法？！？ – 2012-07-31 05:02:43

是的，这不是有效的C＃语法。这只是为了解释我的问题。 – NewBie 2012-07-31 05:03:56

答

安德烈的答案肯定会奏效。你可以概括这分组的概念，并支持IEnumerables任意数量的合并

List<MyEntity> source1 = ...; 
List<MyEntity> source2 = ...; 
IEnumerable<MyEntity> source3 = ...; 

var mergedList = (from item in source1.Contact(source2).Concat(source3) 
        group item by item.Name into g 
        select new MyEntity { Name = g.Key, Value = g.Sum(e => e.Value) }) 
        .ToList();

我刚刚用完整的lambda选项编辑了我的答案，但是这个LINQ选项也非常好。 +1 – 2012-07-31 05:24:36

答

检查了这一点：

public class MyEntity 
{ 
    public string Name { get; set; } 
    public int Value { get; set; } 
} 

public static class MyEntityListExtension 
{ 
    public static List<MyEntity> AddList(this List<MyEntity> FirstList, List<MyEntity> SecondList) 
    { 
     List<MyEntity> ReturnList = new List<MyEntity>(); 

     foreach (MyEntity CurrentEntity in FirstList) 
     { 
      MyEntity TempEntity = SecondList.Where<MyEntity>(x => x.Name.Equals(CurrentEntity.Name)).SingleOrDefault<MyEntity>(); 

      if (TempEntity != null) 
      { 
       ReturnList.Add(new MyEntity() 
       { 
        Name = CurrentEntity.Name, 
        Value = CurrentEntity.Value + TempEntity.Value 
       }); 
      } 
     } 

     return ReturnList; 
    } 
}

用法：

 List<MyEntity> list1 = new List<MyEntity>(); 
     List<MyEntity> list2 = new List<MyEntity>(); 
     List<MyEntity> addedList = new List<MyEntity>(); 

     list1.Add(new MyEntity() 
     { 
      Name = "A", 
      Value = 1 
     }); 

     list1.Add(new MyEntity() 
     { 
      Name = "B", 
      Value = 1 
     }); 

     list2.Add(new MyEntity() 
     { 
      Name = "A", 
      Value = 2 
     }); 


     addedList = list1.AddList(list2);

问候

好球员，我想出了这个第二个解决方案。看，我不是拉姆达专家，所以我只是觉得这太棒了！

public static class MyEntityListExtension 
{ 
    public static List<MyEntity> AddList(this List<MyEntity> FirstList, List<MyEntity> SecondList) 
    { 
     return FirstList.Join<MyEntity, MyEntity, string, MyEntity>(SecondList, x => x.Name, y => y.Name, (x, y) => 
      { 
       return new MyEntity() 
       { 
        Name = x.Name, 
        Value = x.Value + y.Value 
       }; 
      }).ToList<MyEntity>(); 
    } 
}

答

我没有测试的代码，但是这可能给你一些想法....

List<Obj> list1= New List(obj1,obj2); 
List<Obj> list2= New List(obj3,obj4); 

    var allObjects= 
     from list1.Concat(list2); 

    var list3=from o in allObjects 
      group o by o.State into g 
     select new {State=g.key,Value=g.Sum(p => p.Value)}; 

    foreach (var obj in list3) 
    { 
     Console.WriteLine("{0},{1}",obj.State,obj.Value); 
    }

如何比较基于常见字符串值的两个列表？

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