合并C#中的两个列表，并将具有相同ID的对象合并到一个列表项中 [英] Merge two Lists in C# and merge objects with the same id into one list item

问题描述

我已经考虑过如何通过推出自己的解决方案来解决此问题，但是我想知道.NET是否已经具有我要实现的功能-如果是的话，我宁愿使用某些功能内置的.

I have already thought about how I'm going to solve this by rolling my own solution, but I wondered if .NET already has the functionality for what I'm trying to acheive - if so, I'd rather use something built-in.

假设我有一个Widget对象的两个实例，我们称它们为PartA和PartB.来自每个服务的信息都来自两个不同的Web服务，但是两个都有匹配的ID.

Suppose I have two instances of a Widget object, let's call them PartA and PartB. The information from each has been garnered from two different web services, but both have matching IDs.

PartA
{
    ID: 19,
    name: "Percy",
    taste: "",
    colour: "Blue",
    shape: "",
    same_same: "but different"
}

PartB
{
    ID: 19,
    name: "",
    taste: "Sweet",
    colour: "",
    shape: "Hexagon",
    same_same: "but not the same"
}

我想将它们合并以创建以下内容:

I want to merge these to create the following:

Result
{
    ID: 19,
    name: "Percy",
    taste: "Sweet",
    colour: "Blue",
    shape: "Hexagon",
    same_same: "but different"
}

请注意，same_same的值在每个之间是如何不同的，但是我们认为PartA是主文件，因此结果保留了值but different.

Notice how the value for same_same differs between each, but we consider PartA the master, so the result retains the value but different.

现在让事情复杂化

假设我们有两个列表:

List<Widget> PartA = getPartA();
List<Widget> PartB = getPartB();

现在，这里有一些伪代码描述了我想做什么:

Now here's some pseudocode describing what I want to do:

List<Widget> Result = PartA.MergeWith(PartB).MergeObjectsOn(Widget.ID).toList();

推荐答案

您可以编写自己的扩展方法，如下所示:

You could write your own extension method(s), something like this:

static class Extensions
{
    public static IEnumerable<T> MergeWith<T>(this IEnumerable<T> source, IEnumerable<T> other) where T : ICanMerge
    {
        var otherItems = other.ToDictionary(x => x.Key);
        foreach (var item in source)
        {
            yield return (T)item.MergeWith(otherItems[item.Key]);
        }
    }
    public static string AsNullIfEmpty(this string s)
    {
        if (string.IsNullOrEmpty(s))
            return null;
        else
            return s;
    }
}

ICanMerge的位置:

public interface ICanMerge
{
    object Key { get; }
    ICanMerge MergeWith(ICanMerge other);
}

已实施，例如像:

public class Widget : ICanMerge
{
    object ICanMerge.Key { get { return this.ID; } }
    int ID {get;set;}
    string taste {get;set;}
    public ICanMerge MergeWith(ICanMerge other)
    {
        var merged = new Widget();
        var otherWidget = (Widget)other;
        merged.taste = this.taste.AsNullIfEmpty() ?? otherWidget.taste;
        //...
        return merged;
    }
}

然后就像PartA.MergeWith(PartB).ToList()一样简单.

这篇关于合并C#中的两个列表，并将具有相同ID的对象合并到一个列表项中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！