匿名类型的IEqualityComparer

问题描述：

我有这个

 var n = ItemList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList();
 n.AddRange(OtherList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList(););

如果允许的话，我想这样做

I would like to do this if it where allowed

n = n.Distinct((x, y) => x.Vchr == y.Vchr)).ToList();

我尝试使用通用的 LambdaComparer ，但是由于我使用的是匿名类型，因此没有类型与之关联.

I tried using the generic LambdaComparer but since im using anonymous types there is no type associate it with.

请帮我Obi Wan Kenobi，您是我唯一的希望"

"Help me Obi Wan Kenobi, you're my only hope"

答

诀窍是创建一个仅适用于推断类型的比较器.例如:

The trick is to create a comparer that only works on inferred types. For instance:

public class Comparer<T> : IComparer<T> {
  private Func<T,T,int> _func;
  public Comparer(Func<T,T,int> func) {
    _func = func;
  }
  public int Compare(T x,  T y ) {
    return _func(x,y);
  }
}

public static class Comparer {
  public static Comparer<T> Create<T>(Func<T,T,int> func){ 
    return new Comparer<T>(func);
  }
  public static Comparer<T> CreateComparerForElements<T>(this IEnumerable<T> enumerable, Func<T,T,int> func) {
    return new Comparer<T>(func);
  }
}

现在我可以执行以下... hacky解决方案:

Now I can do the following ... hacky solution:

var comp = n.CreateComparerForElements((x, y) => x.Vchr == y.Vchr);

匿名类型的IEqualityComparer

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