c# – 将匿名类型的列表转换为字典>

首先,我建议不要使用List< object>只是…创建一个自定义类.

public class SecurityScore {
    public string Security { get; set; }
    public DateTime Date { get; set; }
    public int ZScore { get; set; }
}

但是,如果出于任何原因需要这样做,请尝试Jon Skeet的这种方法：

I’ve always known that it’s perfectly easy to return an instance of an anonymous type by declaring that the method will return object. However,it hadn’t occurred to me before today that you can actually cast back to that type afterwards. Of course,you can’t just use a normal cast expression – that requires the name of the type to be known at compile-time. But you can do a cast in a generic method… and you can use type inference to supply a type argument… and two anonymous type instance creation expressions will use the same type within the same assembly if the order,names and types of the properties are the same.

如果你想探索他的解决方案,请查看他关于这个主题的blog post.

为了完整起见,我将在此处发布他的代码：

static class GrottyHacks
{
    internal static T Cast<T>(object target,T example)
    {
        return (T) target;
    }
}

class CheesecakeFactory
{
    static object CreateCheesecake()
    {
        return new { Fruit="Strawberry",Topping="Chocolate" };
    }

    static void Main()
    {
        object weaklyTyped = CreateCheesecake();
        var stronglyTyped = GrottyHacks.Cast(weaklyTyped,new { Fruit="",Topping="" });

        Console.WriteLine("Cheesecake: {0} ({1})",stronglyTyped.Fruit,stronglyTyped.Topping);            
    }
}

我必须承认,虽然我不喜欢装箱/取消装箱匿名类型的想法,但他的方法非常棒,占用了相对较少的代码.

所以,既然我已经给你一个可能的解决方案,我必须问 – 为什么你这样做,而不是创建一个简单的类？

编辑：同样为了完整性,我将使用Jon Skeet的解决方案实现您的特定问题：

void Main()
{
    // Create a list of (boxed) anonymous objects
    var securitiesBoxed = new List<object>() {
        new { Security = "6752 JT",Date = DateTime.Parse("1/17/2011 12:00:00 AM"),zScore = 1 },new { Security = "6753 JT",zScore = 2 },new { Security = "6754 JT",zScore = 3 },new { Security = "6752 JT",Date = DateTime.Parse("1/18/2011 12:00:00 AM"),Date = DateTime.Parse("1/19/2011 12:00:00 AM"),zScore = 3 }
    };

    // Now,to convert to a Dictionary<string,double>>...
    var securitiesUnboxed = securitiesBoxed.Select(x => Cast(x,new { Security = "",Date = new DateTime(),zScore = 0 }))
        .GroupBy(x => x.Security)
        .ToDictionary(x => x.Key,x => x.OrderBy(y => y.Date));
}

// This is the static method that will cast our anonymous type
internal static T Cast<T>(object target,T example)
{
    return (T) target;
}

在LINQPad,上面的代码产生以下数据：