合并两个列表的重复项时条件合并答案

【问题标题】：Condition merge while merging duplicate of two List合并两个列表的重复项时条件合并
【发布时间】：2018-10-08 19:28:56
【问题描述】：

我有两个列表，

private List<DealResponse> L1 = new List<DealResponse>
{
    new DealResponse {detailId = "5", detailcd = "ABC", fileName = "string 1", isNgo = "0"},
    new DealResponse {detailId = "5", detailcd = "DEF", fileName = "string 2", isNgo = "0"},
    new DealResponse {detailId = "5", detailcd = "XYZ", fileName = "string ", isNgo = "0"}
};

private List<DealResponse> L2 = new List<DealResponse>
{
    new DealResponse {detailId = "5", detailcd = "ABC", fileName = "string 11", isNgo = "1"},
    new DealResponse {detailId = "6", detailcd = "MNO", fileName = "string 3", isNgo = "1"}
};

我正在尝试编写一个接受detailId并通过合并以上两个列表返回结果的方法，如果有重复（重复定义=两个列表之间的detailId，detailcd匹配时）从L2中选择条目

所以合并后的结果就是

var Result = new List<DealResponse>
{
    new DealResponse {detailId = "5", detailcd = "ABC", fileName = "string 11", isNgo = "1"},
    new DealResponse {detailId = "5", detailcd = "DEF", fileName = "string 2", isNgo = "0"},
    new DealResponse {detailId = "5", detailcd = "XYZ", fileName = "string ", isNgo = "0"},
    new DealResponse {detailId = "6", detailcd = "MNO", fileName = "string 3", isNgo = "1"},
};

请注意，由于 detailId = 5，detailcd = ABC 是重复的，因此我们从 L2 中选择了这个条目

public List<DealResponse> GetDealResponse(string detailId)   
{
    // My main confusion is while doing union how to handle the case 
    // which I mentioned (On duplicate select entry from second list)  
    var L3 = L1.Union(L2, new DealResponseComprarer()).ToList();         
}  

public class DealResponse
{
    public string detailId { get; set; }
    public string detailcd { get; set; }
    public string fileName { get; set; }
    public string isNgo { get; set; }
}

public class DealResponseComprarer : IEqualityComparer<DealResponse>
{
    public bool Equals(DealResponse x, DealResponse y)
    {
        return x.detailId == y.detailId &&  x.detailcd == y.detailcd ;
    }

    public int GetHashCode(DealResponse obj)
    {
        return (obj.detailId.GetHashCode() + obj.detailcd.GetHashCode());
    }
}

【问题讨论】：

试试var L3 = L2.Union(L1, new DealResponseComprarer()).ToList();
@Matt.G 在这种情况下，如何确保当有重复项时我从 L2 中选择一个条目。如果您在有重复结果时查看结果应该包括来自 L2 的条目
我听不懂你的GetDealResponse(int detailId)。 detailId 如何在这里发挥作用？结果列表不应包含具有detailId = 6 的元素，而应仅包含具有detailId = 5 的Distinct 元素（例如），具有L2 优先级。
当您的方法将int 用于detailId 时，这会让人感到困惑，但它在DealResponse 类中被声明为string。
@RufusL 抱歉，这是我的错误，已更正。谢谢

标签： c# list linq merge

【解决方案1】：

我正在尝试编写一个接受detailId并通过合并以上两个列表返回结果的方法，如果有重复（重复定义=两个列表之间的detailId，detailcd匹配时）从L2中选择条目

另一种说法是：

从 L2 开始
添加 L1 中尚未在 L2 中的所有内容

这可以用一行来完成：

var combined = L2.Concat(L1.Except(L2, new DealResponseComprarer()));

Example on DotNetFiddle

【讨论】：

【解决方案2】：

如果您确实想使用detailId 过滤结果，由于此值已传递给GetDealResponse() 方法，您可以将.Where 条件添加到均衡的Union 列表中。

public class DealResponse
{
    public string detailId { get; set; }
    public string detailcd { get; set; }
    public string fileName { get; set; }
    public string isNgo { get; set; }
}

public List<DealResponse> GetDealResponse(string detailId)
{
    return L2.Union(L1, new DealResponseComprarer())
             .Where(elm => elm.detailId.Equals(detailId)).ToList();
}


L1 = new List<DealResponse>() {
new DealResponse() { detailId = "5", detailcd = "ABC" , fileName = "string 1", isNgo = "0" },
new DealResponse() { detailId = "5", detailcd = "DEF" , fileName = "string 2", isNgo = "0" },
new DealResponse() { detailId = "5", detailcd = "XYZ" , fileName = "string ", isNgo = "0" }};

L2 = new List<DealResponse>() {
new DealResponse() { detailId = "5", detailcd = "ABC" , fileName = "string 11", isNgo = "1" },
new DealResponse() { detailId = "6", detailcd = "MNO" , fileName = "string 3", isNgo = "1" }};

string ID = "5";
List<DealResponse> L3 = GetDealResponse(ID);

这将返回此列表：

{ detailId = "5", detailcd = "ABC" , fileName = "string 11", isNgo = "1" }
{ detailId = "5", detailcd = "DEF" , fileName = "string 2", isNgo = "0" }
{ detailId = "5", detailcd = "XYZ" , fileName = "string ", isNgo = "0" }

【讨论】：

@Ami 代码已修改。测试它以查看它是否返回您期望的结果。（顺便说一句，你这里有一个错字：DealResponseComprarer : IEqualityComparer<DealResponse>）。
您的解决方案解决了我的问题。谢谢。此外，我尝试投票并接受它，但看起来我需要至少 15 名声望才能做到这一点。