C#通过id合并多个列表并对属性求和

Question

我有一个如下所示的图形类：

public class Graphic
{
    public int id { get; set; }
    public int Counter { get; set; }
}

现在我有 3 个 grapic 列表：

public void myFunction()
{
    List<Graphic> l1= new List<Graphic> ();
    List<Graphic> l2= new List<Graphic> ();
    List<Graphic> l3= new List<Graphic> ();

    l1.Add(new Graphic {id = 1, Counter = 4});
    l1.Add(new Graphic {id = 2, Counter = 2});
    l1.Add(new Graphic {id = 3, Counter = 9});
    l1.Add(new Graphic {id = 4, Counter = 1});

    l2.Add(new Graphic {id = 1, Counter = 1});
    l2.Add(new Graphic {id = 2, Counter = 2});
    l2.Add(new Graphic {id = 3, Counter = 3});
    l2.Add(new Graphic {id = 5, Counter = 1});

    l3.Add(new Graphic {id = 1, Counter = 12});
    l3.Add(new Graphic {id = 7, Counter = 1});
    l3.Add(new Graphic {id = 8, Counter = 3});
    l3.Add(new Graphic {id = 4, Counter = 1});
}

我需要一个代码来合并这 3 个列表，每个图形及其 ID 和计数器属性将被汇总，因此结果将是：

var mergedList = {
    Graphic {id = 1, Counter = 17},
    Graphic {id = 2, Counter = 4},
    Graphic {id = 3, Counter = 12},
    Graphic {id = 4, Counter = 2},
    Graphic {id = 5, Counter = 1},
    Graphic {id = 7, Counter = 1},
    Graphic {id = 8, Counter = 3}
}

任何想法都会帮助我。 有没有办法使用 LINQ 有效地做到这一点？

Answer 1

使用.Concat合并3个列表，然后GroupBy得到不同ids的所有Counter值：

var result = l1.Concat(l2)
               .Concat(l3)
               .GroupBy(item => new { item.id, item.Geometry }, item => item.Counter)
               .Select(group => new Graphic
               {
                   id = group.Key,
                   Counter = group.Sum()
               }).ToList();

请参阅集合初始化器以更简洁地初始化列表：

List<Graphic> l1 = new List<Graphic>
{
    new Graphic { id = 2, Counter = 2 },
    new Graphic { id = 3, Counter = 9 },
    new Graphic { id = 4, Counter = 1 },
    new Graphic { id = 1, Counter = 4 },
};

我还建议阅读 C# naming conventions 以了解函数和属性的命名。