在子查询LINQ中选择一个元素(Select One element in a subquery LINQ)

在子查询LINQ中选择一个元素(Select One element in a subquery LINQ)

我正在使用LINQ从数据库中提取数据，并且有一个关于从子查询中提取对象的问题。 这是我正在拉的班级：

public class Users { public Users() { SerialNumbers = new HashSet<SerialNumbers>(); } /// <summary> /// The User's Unique Id /// </summary> public Guid Id { get; set; } /// <summary> /// The Users name /// </summary> public string Name { get; set; } /// <summary> /// The Users email. This can be null/empty string /// </summary> public string Email { get; set; } public virtual ICollection<SerialNumbers> SerialNumbers { get; set; } }

如何从Serial Numbers集合中选择第一个元素，而不是整个集合本身？

谢谢

I am using LINQ to pull data from a database and have a question about pulling an object from a subquery. This is the class that I am pulling:

public class Users { public Users() { SerialNumbers = new HashSet<SerialNumbers>(); } /// <summary> /// The User's Unique Id /// </summary> public Guid Id { get; set; } /// <summary> /// The Users name /// </summary> public string Name { get; set; } /// <summary> /// The Users email. This can be null/empty string /// </summary> public string Email { get; set; } public virtual ICollection<SerialNumbers> SerialNumbers { get; set; } }

How do I select the first element from the Serial Numbers collection and not the whole collection itself?

Thanks

最满意答案

您应该创建一个DataTransferObject并映射到它：

context.Users.Select(x => new UserDto { Id = x.Id, Name = x.Name, Email = x.Email, SerialNumber = x.SerialNumbers.FirstOrDefault() });

You should make a DataTransferObject and map to it:

context.Users.Select(x => new UserDto { Id = x.Id, Name = x.Name, Email = x.Email, SerialNumber = x.SerialNumbers.FirstOrDefault() });