30秒学会 C# 片段 – SymmetricDifferenceBy

Returns the symmetric difference betweend two collections, after applying the provided function to each element of both.

Use IEnumerable.Select() to map each element of either collection to the desired type.
Use IEnumerable.Except() to only return elements in one enumerable object and not the other.
Use IEnumerable.Union() to combine the result of applying that to each object.

代码实现

using System.Collections.Generic;
using System.Linq;

public static partial class _30s 
{
  public static IEnumerable<R> SymmetricDifferenceBy<T,R>(IEnumerable<T> a, IEnumerable<T> b, Func<T,R> map) 
  {
    IEnumerable<R> mapA = a.Select(map);
    IEnumerable<R> mapB = b.Select(map);
    return mapA.Except(mapB).Union(mapB.Except(mapA));
  }
}

使用样例

var p = new[] {
  new { a = 3, b = 2},
  new { a = 2, b = 1}
};
var q = new[] {
  new { a = 6, b = 2},
  new { a = 6, b = 3}
};

_30s.SymmetricDifferenceBy(p, q, x => x.b); // { 1, 3 }