c# 使用 linq 获取具有相同值的对象元素

Question

我有两个名为 LastFiles 和 DbObj 的对象。当我提取数据时，我有 2 个由这些组成的对象列表。我创建了一个这样的场景。

public class LastFiles
{
    public int Id { get; set; }
    public string Title { get; set; }
    public string Author { get; set; }
    public string Translator { get; set; }
    public string Supervisor { get; set; }
    public string Type { get; set; }
    public string FileName { get; set; }
    public string ModifiedDate { get; set; }
}

public class DbObj
{
    public int Id { get; set; }
    public int WorkId { get; set; }
    public string Type { get; set; }
    public int TypeId { get; set; }
}

var lastFiles = new List<LastFiles> {
    new LastFiles { Id = 1, Title = "Title 1", Author = "Author 1", Type = "book", FileName = "file-name-1.pdf" },
    new LastFiles { Id = 2, Title = "Title 2", Author = "Author 2", Type = "book", FileName = "file-name-2.pdf" },
    new LastFiles { Id = 3, Title = "Title 3", Author = "Author 3", Type = "article", FileName = "file-name-3.pdf" },
    new LastFiles { Id = 4, Title = "Title 4", Author = "Author 4", Type = "article", FileName = "file-name-4.pdf" },
    new LastFiles { Id = 5, Title = "Title 5", Author = "Author 5", Supervisor = "Supervisor 1", Type = "thesis", FileName = "file-name-5.pdf" },
    new LastFiles { Id = 6, Title = "Title 6", Author = "Author 6", Supervisor = "Supervisor 2", Type = "thesis", FileName = "file-name-6.pdf" }
};

var dbObj = new List<DbObj> {
    new DbObj { Id = 1, WorkId = 5, Type = "book", TypeId = 1 },
    new DbObj { Id = 2, WorkId = 5, Type = "book", TypeId = 2 },
    new DbObj { Id = 3, WorkId = 5, Type = "thesis", TypeId = 5 },
    new DbObj { Id = 4, WorkId = 5, Type = "thesis", TypeId = 6 },
    new DbObj { Id = 5, WorkId = 278, Type = "article", TypeId = 689 }
};

如果我必须经历这个场景；如何从 lastFiles 获取 LastFiles.Type 值与 DbObj.Type 值和 LastFiles.Id 相同的项目 与 DbObj.TypeId 相同吗？

Answer 1

您可以使用匿名对象来连接两个集合，如下所示:

var result = (from lf in lastFiles
                      join db in dbObj on new { lf.Type, TypeId = lf.Id}
                                   equals new  { db.Type, db.TypeId} 
                      select lf).ToList();

编辑

联接的 Lambda 版本:

var result2 = lastFiles.Join(dbObj,lf=> new {lf.Type,TypeId = lf.Id},db=>new  { db.Type,db.TypeId},(lf,db)=> lf  ).ToArray();

Fiddle

请注意，属性名称和类型应匹配。您可能需要在实际代码中进行重命名和转换。