在c# 3.0中,您可以使用以下语法创建匿名类

var o = new { Id = 1, Name = "Foo" };

有没有办法将这些匿名类添加到泛型列表中?

例子:

var o = new { Id = 1, Name = "Foo" };
var o1 = new { Id = 2, Name = "Bar" };

List<var> list = new List<var>();
list.Add(o);
list.Add(o1);

另一个例子:

List<var> list = new List<var>();

while (....)
{
    ....
    list.Add(new {Id = x, Name = y});
    ....
}

当前回答

使用反射

关于此主题的Microsoft文档。

using System;
using System.Collections;
using System.Collections.Generic;

var anonObj = new { Id = 1, Name = "Foo" };
var anonType = anonObj.GetType();

var listType = typeof(List<>);

// We know that List<> have only one generic argument, so we do this:
var contructed = listType.MakeGenericType(anonType);

// Create instance
var instance = Activator.CreateInstance(contructed);

// Using it
var list = (IList)instance;
list.Add(anonObj);

对于Dictionary<,>,您需要传递2个参数 例:dicType。MakeGenericType(type1, type2)

对于带有约束的泛型类型(其中T: struct), 我们需要做更多的核实。查看微软文档来学习如何操作。

其他回答

您可以在代码中这样做。

var list = new[] { new { Id = 1, Name = "Foo" } }.ToList();
list.Add(new { Id = 2, Name = "Bar" });

我检查了几个答案的IL。这段代码有效地提供了一个空列表:

    using System.Linq;
    …
    var list = new[]{new{Id = default(int), Name = default(string)}}.Skip(1).ToList();

根据这个答案,我提出了两种可以完成任务的方法:

    /// <summary>
    /// Create a list of the given anonymous class. <paramref name="definition"/> isn't called, it is only used
    /// for the needed type inference. This overload is for when you don't have an instance of the anon class
    /// and don't want to make one to make the list.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="definition"></param>
    /// <returns></returns>
#pragma warning disable RECS0154 // Parameter is never used
    public static List<T> CreateListOfAnonType<T>(Func<T> definition)
#pragma warning restore RECS0154 // Parameter is never used
    {
        return new List<T>();
    }
    /// <summary>
    /// Create a list of the given anonymous class. <paramref name="definition"/> isn't added to the list, it is
    /// only used for the needed type inference. This overload is for when you do have an instance of the anon
    /// class and don't want the compiler to waste time making a temp class to define the type.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="definition"></param>
    /// <returns></returns>
#pragma warning disable RECS0154 // Parameter is never used
    public static List<T> CreateListOfAnonType<T>(T definition)
#pragma warning restore RECS0154 // Parameter is never used
    {
        return new List<T>();
    }

你可以使用这些方法

var emptyList = CreateListOfAnonType(()=>new { Id = default(int), Name = default(string) });
//or
var existingAnonInstance = new { Id = 59, Name = "Joe" };
var otherEmptyList = CreateListOfAnonType(existingAnonInstance);

这个答案也有类似的想法,但直到我创建了这些方法之后我才发现它。

我很惊讶居然没有人建议集合初始化器。这种方法只能在创建列表时添加对象,因此得名,但它似乎是最好的方法。不需要创建一个数组,然后将其转换为列表。

var list = new List<dynamic>() 
{ 
    new { Id = 1, Name = "Foo" }, 
    new { Id = 2, Name = "Bar" } 
};

你可以总是使用对象而不是动态,但尽量保持在一个真正的通用方式,那么动态更有意义。

下面是另一种创建匿名类型列表的方法,它允许你从一个空列表开始,但仍然可以访问智能感知。

var items = "".Select( t => new {Id = 1, Name = "foo"} ).ToList();

如果您想保留第一项,只需在字符串中放入一个字母。

var items = "1".Select( t => new {Id = 1, Name = "foo"} ).ToList();