在多個值上相交兩個物件串列

假設我有兩個相同類別的串列。

public class emailfilter
{
 public string from {get;set;}
 public string to {get;set;}
 public string cc {get;set;}
 public string subj {get;set;}
 public string body {get;set;}
 public string emailid {get;set;}
}
//there are two lists of type emailfilter. 1 list is formed dynamically from the config file
List<emailfilter> configfilterlist = //mock sudo code//
{
efilter tempobj = new efilter();
tempobj.from = config.from or "" if no value
tempobj.to = config.to or "" if no value
tempobj.cc = config.cc or "" if no value
tempobj.subj = config.subj or "" if no value
tempobj.body = config.body or "" if no value
configfilterlist.add(tempobj);
}
//List1 will never have an emailID
//List2 is formed from email items pulled from exchange and made into efilter objects and those do have an emailid.
//List2 will typically have all object fields populated. List1, the object fields are optional

因此，我想將過濾器專案的 list1 與電子郵件專案的 list2 進行比較/相交，以形成一個沒有重復項的組合串列，該串列僅包含具有 list1 的所有過濾條件并包含 list2 的 mailid 的專案。如果 List1 上的值沒有值，我想忽略它，只匹配提供的配置值，跳過任何 "" 空白字串。我希望有一種方法可以使用 lambda 和 linq 來做到這一點，但我還沒有看到任何關于多個值的比較示例，并且在這種情況下忽略了其他類似 emailID 的示例。

更新：感謝@wertzui 提供解決此問題所需的答案。最終的解決方案略有不同，因此基本上用最終的解決方案更新帖子/問題，以防它幫助另一個迷失的靈魂。

public class emailfilter: IEquatable<emailfilter>
{
    public string from { get; set; }
    public string to { get; set; }
    public string cc { get; set; }
    public string subj { get; set; }
    public string body { get; set; }
    public string emailid { get; set; }
    
    public override int GetHashCode()
    {
        return System.HashCode.Combine(from, to, cc, subj, body);
    }
    
    public override bool Equals(object? obj) => Equals(obj as emailfilter);

    public bool Equals(emailfilter? other)
    {
        return
            other != null &&
            (from.Contains(other.from) || other.from == "") &&
            (to.Contains(other.sentto) || other.to == "") &&
            (cc.Contains(other.cc) || other.cc == "") &&
            (subj.Contains(other.subj) || other.subj == "") &&
            (body.Contains(other.body) || other.body == "");
    }
}

//emailsasfilters is List2 = all exchange emails as filter objects
var combinedSet = new HashSet<emailfilter>();
foreach (var filter in configfilterlist)  //configfilterlist is List1 = filters from Config
{
                    if (emailsasfilters.Contains(filter))
                    combinedSet.Add(emailsasfilters.ElementAt(emailsasfilters.IndexOf(filter)));
}
combinedSet.Dump();

uj5u.com熱心網友回復：

從 .Net 6 開始，UnionBy您可以使用一種新方法。

var combined = configfilterlist
    .UnionBy(
        exchangefilterlist, 
        e => new { e.from, e.to, e.cc, e.subj, e.body })
    .ToList();

另一種適用于舊框架版本的方法是，使用HashSet<T>并實作GetHashCode和Equals

public class emailfilter: IEquatable<emailfilter>
{
    public string from { get; set; }
    public string to { get; set; }
    public string cc { get; set; }
    public string subj { get; set; }
    public string body { get; set; }
    public string emailid { get; set; }
    
    public override int GetHashCode()
    {
        return System.HashCode.Combine(from, to, cc, subj, body);
    }
    
    public override bool Equals(object? obj) => Equals(obj as emailfilter);

    public bool Equals(emailfilter? other)
    {
        return
            other != null &&
            from == other.from &&
            to == other.to &&
            cc == other.cc &&
            subj == other.subj &&
            body == other.body;
    }
}

var combinedSet = new HashSet<emailfilter>(configfilterlist);
foreach (var email in exchangefilterlist)
{
    combinedSet.Add(email);
}
combinedSet.Dump();

標籤：C＃ 林克 拉姆达

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