使用LINQ时出错 [英] Error when using LINQ

问题描述

var q = (from t1 in Bank.Users join t2 in Bank.Questions on t1.Id equals t2.Id_Users select new { t1.Id, t1.Name }).ToList();
      List<object> d = new List<object>();
      d = q.ToList();

d = q.ToList();//错误

我试图将其翻译成英语，但是OP并没有实际询问任何问题，他只是说谁可以回答这个问题".

d = q.ToList();// Error

I attempted to translate this to English, but the OP did not actually ask anything, he just said ''who can answer this question''.

推荐答案

让我们" s使它更具可读性，而不仅仅是将其保留在对象中.
有一个名为UserInfo 的类或结构(假设").

Let''s make it more readable than just keeping it in objects.
Have a class or a struct called UserInfo (lets'' assume).

public class UserInfo
{
     public int Id { get;set; }
     public string Name { get;set; }
}

定义列表/枚举.

Define the list/enumeration.

List<UserInfo> d = new List<UserInfo>();

稍微更改您的查询.

Slightly alter your query.

var q = (from t1 in Bank.Users
         join t2 in Bank.Questions
         on t1.Id equals t2.Id_Users
         select new UserInfo
         {
           Id = t1.Id,
           Name = t1.Name
         });

现在，q是IEnumerable<UserInfo>.您可以使用.ToList()方法将其转换为列表.

Now, q is an IEnumerable<UserInfo>. You can convert it to list using .ToList() method.

d = q.ToList();

请以英文发布.

您已经致电ToList. q是一个列表. List没有ToList方法，因为它将是多余的.

Please post in English.

You already called ToList. q is a list. List does not have a ToList method, as it would be redundant.

List<object> d = new List<object>();
      d = q.ToList();

鉴于它是List< var> ;，不是List< object>.这也没有意义.您创建一个新列表，然后将其丢弃.

This may well break it too, given that it''s a List<var> not a List<object>. It''s also pointless. You create a new list, then discard it.

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