当底层匿名类型相似时，如何在Linq中连接两个列表

本文关键字：连接 Linq 列表 两个 类型 相似 | 更新日期: 2023-09-27 17:54:59

考虑以下代码:

var listA = from s in Students 
            select new {FirstName= s.FirstName, LastName = s.LastName};
var listB = from t in Teachers 
            select new {FirstName= t.FirstName, LastName = t.LastName};

var teachersAndStudents = listA.Concat(listB); // This fails because types are not same
var someName = teachersAndStudents.First().FirstName;

如何创建teachersAndStudents列表而不丢失类型?

不丢失类型意味着teachersAndStudents.First().FirstName应该在最后一行有效。

当底层匿名类型相似时，如何在Linq中连接两个列表

这段代码运行良好，你的问题在别的地方

   class Student
    {
        public string FirstName { get; set; }
        public string LastName { get; set; } 
    }
    class Teacher
    {
        public string FirstName { get; set; }
        public string LastName { get; set; } 
    }
    class Program
    {
        static void Main(string[] args)
        {
            var listA = from s in new List<Student>()
                        select new { FirstName = s.FirstName, LastName = s.LastName };
            var listB = from t in new List<Teacher>()
                        select new { FirstName = t.FirstName, LastName = t.LastName };
            var teachersAndStudents = listA.Concat(listB); 
            var someName = teachersAndStudents.First().FirstName;
        }
    }

调用Concat的行不会因为类型而失败，因为两个匿名类型是相同的。试试这段代码，你也会看到:

var listA = from s in Students
            select new { FirstName = s.FirstName, LastName = s.LastName };
var listB = from t in Teachers
            select new { FirstName = t.FirstName, LastName = t.LastName };
Console.WriteLine(listA.First().GetType().Name);
Console.WriteLine(listB.First().GetType().Name);
在我的例子中，这段代码输出: 
<>f__AnonymousType0`2
<>f__AnonymousType0`2

这证明编译器已经为要求匿名类型的语句生成了相同的实际类型。

你能附加你收到的错误吗?

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