我可以使用LINQ比较两个集合之间缺少，添加或更新的内容吗 [英] Can I use LINQ to compare what is missing, added or updated between two collections

问题描述

我有以下课程.为了做到这一点，我可以比较一下，我添加了一个Equals方法:

I have the following class. To make it so I could compare I added an Equals method:

 public ObjectiveDetail()
    public int ObjectiveDetailId { get; set; }
    public int Number { get; set; }
    public string Text { get; set; }
    public override bool Equals(object obj)
    {
        return this.Equals(obj as ObjectiveDetail);
    }
    public bool Equals(ObjectiveDetail other)
    {
        if (other == null)
            return false;

        return this.Number.Equals(other.Number) &&
            (
                this.Text == other.Text ||
                this.Text != null &&
                this.Text.Equals(other.Text)
            );
    }
 }

我有两个ICollection集合:

I have two ICollection collections:

ICollection<ObjectiveDetail> _obj1; // Reference
ICollection<ObjectiveDetail> _obj2; // May have more, less or different objectDetails from the reference.

集合的通用tfield是ObjectiveDetailId.有没有一种方法可以使用三个LINQ表达式来创建:

The common tfield with the collections is ObjectiveDetailId. Is there a way I can use three LINQ expressions to create:

• _obj2中而不是_obj1中的行的集合
• _obj1中而不是_obj2中的行的集合
• _obj1和_obj2之间不同的行的集合

请注意，这类似于我之前问的另一个问题，但是我认为现在添加了Equals方法，这有点简单.应该这样做吗?

Note this is similar to another question I asked earlier but I think this is a bit simpler now I have added the Equals method. uld do this?

推荐答案

您可以使用

You can use Except to subtract sets:

var in2butNot1 = _obj2.Except(_obj1);
var in1butNot2 = _obj1.Except(_obj2);

但是，这可能并不是您想要得到的，因为已更改"的对象将被视为彼此不相等".

However, this may not be what you are looking to get, because objects that have "changed" will be treated as simply "not equal" to each other.

看来您的对象有一个ID字段.您可以在该ID上对对象进行排序，然后遍历两个集合，就好像您正在生成合并一样.这样，您就可以使用简单的if链来检测插入，更新和删除.

It appears that your objects have an ID field. You can order the objects on that ID, and then traverse both collections as if you were producing a merge. This would let you detect insertions, updates, and deletions with a straightforward chain of ifs.

您还可以使用ID来确定什么是共同的，什么是改变的:

You can also use IDs to decide what's common and what's changed:

var ids1 = new HashSet<int>(_obj1.Select(o => o.ObjectiveDetailId));
var ids2 = new HashSet<int>(_obj2.Select(o => o.ObjectiveDetailId));
var in2butNot1 = _obj2.Where(o => !ids1.Contains(o.ObjectiveDetailId));
var in1butNot2 = _obj1.Where(o => !ids2.Contains(o.ObjectiveDetailId));

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