C＃List< object> .RemoveAll（） - 如何删除列表的子集？ [英] C# List<object>.RemoveAll() - How to remove a subset of the list?

问题描述

我有2个类别 feeds_Auto 和产品，具有多个匹配属性。对于这个特殊的问题，AutoID是唯一需要使用的字段。

I have a 2 classes feeds_Auto and Product with multiple matching properties. For this particular problem, the AutoID is the only field I need to use.

我有一个列表< FeedsAuto> 和几百个我有一个小的列表<产品> 与10,20个独特的条目。我现在要从大列表中删除小列表中的所有项目。

I have a List<FeedsAuto> with several hundred unique entries. I have a small List<Product> with 10, 20 unique entries. I now want to remove all items in the small list from the large list.

如何使用RemoveAll（{lambda expression}）来完成此操作？我发现的所有例子取决于通用列表是简单类型（字符串，整数，等）。

How do I use RemoveAll({lambda expression}) to accomplish this? All of the examples I have found depend on the generic list being of simple types (strings, ints, etc).

private static int DoInserts(ref List<Model.feeds_Auto> source, ref List<Model.Product> target, Guid companyID)
{
    List<Model.Product> newProductList = new List<Model.Product>();
    List<Model.Product> dropSourceList = new List<Model.Product>();

    using (var db = Helpers.GetProdDB())
    {
        foreach (var src in source)
        {
            var tgt = target.Where(a => a.alternateProductID == src.AutoID && a.LastFeedUpdate < src.DateModified).FirstOrDefault();
            if (tgt == null)
            {
                newProductList.Add(new Model.Product{...});
                dropSourceList.Add(src);
            }
        }
        db.SaveChanges();

        if (dropSourceList.Count > 0)
        {
            source.RemoveAll(????);
        }
    }
}

是不难的：

foreach (var drop in dropSourceList)
{
    source.RemoveAll(a => a.AutoID == drop.AutoID);
}

推荐答案

您可以使用 Any 以简化

source.RemoveAll(a => dropSourceList.Any(b => a.AutoID == b.AutoID));

您可以通过创建 HashSet ID of first：

You can reduce the looping by creating a HashSet of ID's first:

var toRemove = new HashSet<int>(dropSourceList.ConvertAll(a => a.AutoID));

source.RemoveAll(a => toRemove.Contains(a.AutoID));

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