在具有相同属性值的两个列表中选择两个比较器
在具有相同属性值的两个列表中选择两个比较器
提问于 2019-02-19 03:31:54
我想要比较两个List<Candidate>，并在Hash属性中选择具有相同值的两个实体。
public class Candidate : IEquatable<Candidate>
{
public string Name { get; set; }
public String Hash { get; set; }
}
//....
//List with "CandidateA", "CandidateB", "CandidateC" values
List<Candidate> newsCandidate = loadNewsCandidate();
//List with "CandidateC' " , "CandidateD", "CandidateE" values
List<Candidate> previousCandidate = loadPreviousCandidate();
//CandidateC and CandidateC' has same 'Hash' value.
//This return "CandidateC" in newsCandidate
var common = newsCandidate.Where(n => previousCandidate.Any(p => p.Hash.Equals(n.Hash))).ToList();我希望检索一个具有n.CandidateC和p.CandidateC'元素的List<Tuple<Candidate,Candidate>>或类似的对象，并输出类似如下的消息：
$"Previous Name: {p.CandidateC.Name} to New Name: {n.CandidateC.Name}"会感谢任何帮助。
回答 2
Stack Overflow用户
发布于 2019-02-19 03:47:33
也许最简单的做法是从以前的候选者创建一个Dictionary并查找每个匹配项：
var prevDict = previousCandidate.ToDictionary(pc => pc.Hash);
var ans = newsCandidate.Select(nc => prevDict.TryGetValue(nc.Hash, out var pc) ? new { pc, nc } : null).Where(pcnc => pcnc != null);如果你不喜欢手动构建你自己的Dictionary，你也可以使用LINQ Join来做同样的事情：
var ansj = previousCandidate.Join(newsCandidate, pc => pc.Hash, nc => nc.Hash, (pc, nc) => new { pc, nc });Stack Overflow用户
发布于 2019-02-19 03:51:15
看起来GroupBy可能会很有用：
var p = new List<Candidate>
{
new Candidate { Name = "John", Hash = "1" },
new Candidate { Name = "Mike", Hash = "2" }
};
var n = new List<Candidate>
{
new Candidate { Name = "Mike", Hash = "1" },
new Candidate { Name = "John", Hash = "2" }
};
var joined = p.Concat(n).GroupBy(item => item.Hash);
Console.WriteLine(string.Join("\n", joined
.Where(g => g.Count() == 2)
.Select(g => $"Old name {g.First().Name}, New name {g.Last().Name}")));
// Old name John, new name Mike
// Old name Mike, new name John或者只需使用以下命令来制作List<Tuple<Candidate, Candidate>>：
List<Tuple<Candidate, Candidate>> tuple = joined
.Where(g => g.Count() == 2)
.Select(g => new Tuple<Candidate, Candidate>(g.First(), g.Last()))
.ToList();页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54754142
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