仅通过特定键 C# 的值将两个字典列表相交

Question

我有两个不同长度的字典列表。两个字典中的键相同，值可能不同。

var A = List<Dictionary<string, object>>();
var B = List<Dictionary<string, object>>();

我想根据其中包含的字典对象中的 3 个键的值将 A 和 B 相交。

例如：

var dict = new Dictionary<string,object>{{"W",val1},{"X",val2},{"Y",val3},{"Z",val4}}

与上述类似的字典包含在列表 A 和 B 中，其中 val1、val2、val3、val4 的值各不相同。如果键 W、X、Y 的值相等，我想使 A 和 B 相交，但我不关心 Z 中的值是否相交。有没有办法优雅地实现这一点？

举例说明：

   A.add(new Dictionary<string,object>{{"W",123},{"X",456},{"Y",789},{"Z",103}});
   A.add(new Dictionary<string,object>{{"W",124},{"X",456},{"Y",789},{"Z",893}});
   A.add(new Dictionary<string,object>{{"W",123},{"X",456},{"Y",789},{"Z",134}});

   B.add(new Dictionary<string,object>{{"W",123},{"X",456},{"Y",789},{"Z",900}});
   B.add(new Dictionary<string,object>{{"W",124},{"X",456},{"Y",789},{"Z",893}});
   B.add(new Dictionary<string,object>{{"W",212},{"X",321},{"Y",789},{"Z",134}});

如果我执行 A.intersect(B)，我希望得到以下列表，

{"W",123},{"X",456},{"Y",789},{"Z",103}
{"W",123},{"X",456},{"Y",789},{"Z",900}
{"W",124},{"X",456},{"Y",789},{"Z",893}

Answer 1

这会给你一个 IEnumerable：

var c=A.Select(a=>new {W=a[W],X=a[X],Y=a[Y]})
  .Intersect(B.Select(a=>new {W=a[W],X=a[X],Y=a[Y]}));

或者，为自己创建一个自定义 IEqualityComparer，然后您可以这样做：

var c=A.Intersect(B,new MyComparer());

类似：

class MyComparer : IEqualityComparer<Dictionary<string,object>>
{
    public bool Equals(Dictionary<string,object> b1, Dictionary<string,object> b2)
    {
        if (b2 == null && b1 == null)
           return true;
        else if (b1 == null || b2 == null)
           return false;
        else if(b1["W"]==b2["W"] && b1["X"]==b2["X"] && b1["X"]==b2["X"])
            return true;
        else
            return false;
    }

    public int GetHashCode(Dictionary<string,object> bx)
    {
        int hCode = bx["W"] ^ bx["X"] ^ bx["Y"];
        return hCode.GetHashCode();
    }
}