如何对具有动态对象的列表进行排序 [英] How to sort a list having dynamic object

问题描述

问题背景：我有一个

BindingList<T>

的动态对象。这些对象属于在运行时创建的某种类。此类可以包含1个或2个或3个或更多属性。每次创建此类时，这些属性的名称也可能不同。

例如

of dynamic objects. These objects are of some type of class which is created at runtime. This class can have 1 or 2 or 3 or more properties. Names of these properties can also be different everytime when this class is created.
e.g.

Class Data
{
Property Value1;
Property Value2;
Property Value3;
..
...
}

下次此课程可以

Next time this class can be

Class Data
{
Property Value1;
Property Value2;
}

问题是：根据某些参数，我可以从用户那里获得一个值'值1。然后我想在属性''Value1''的值上对这个动态对象列表进行排序。

Issue is: Based on some parameter I can get a value from user ''Value1''. Then I want to sort this list of dynamic objects on value of property ''Value1''.

推荐答案

你需要实现一个Comparer [ ^ ]，并将其传递给列表.Sort [ ^ ]方法。

但是由于你有动态对象，你需要使用反射来获取值。使用这个 [ ^ ]方法：

You need to implement a Comparer[^], and pass it to the List.Sort[^] method.
But since you have dynamic objects, you need to use reflection to get the values. Use this[^] approach:

public class DynamicSerializableComparer : IComparer<object>
{
    string _property;

    public DynamicSerializableComparer(string property)
    {
        _property = property;
    }

    public int Compare(object stringA, object stringB)
    {
        string valueA = stringA.GetType().GetProperty(_property).GetValue();
        string valueB = stringB.GetType().GetProperty(_property).GetValue();

        return String.Compare(valueA, valueB);
    }

}

当然，如果您拥有的属性不是字符串或不能与字符串相比，您应该更改相应的最后陈述。



[更新：一些改进和样本]

正如我所提到的，你不能使用 OrderBy ，因为你没有在lambda表达式中指定的属性。

Of course, if the property you have is not string or not comparable as string, you should change the last statement accordingly.

[Update: some improvements, and a sample]
As I mentioned, you can''t use OrderBy, since there is no property you can specify in the lambda expression.

public class DynamicSerializableComparer : IComparer<object>
{
    string _property;

    public DynamicSerializableComparer(string property)
    {
        _property = property;
    }

    public int Compare(object stringA, object stringB)
    {
        string valueA = (string)stringA.GetType().GetProperty(_property).GetValue(stringA, null);
        string valueB = (string)stringB.GetType().GetProperty(_property).GetValue(stringB, null);

        return String.Compare(valueA, valueB);
    }
}

void Main()
{
    var a1 = new { id = 1, name="Peter", email="[e-mail]"};
    var a2 = new { id = 2, name="John", address="USA"};
    var a3 = new { id = 3, name="Robert", address="France"};
    var a4 = new { id = 4, name="Albert", position="Boss"};

    var a = new List<object> {a1, a2, a3, a4};

    a.Sort(new DynamicSerializableComparer("name"));

    a.Dump();
}

此示例将直接在 LinqPad [ ^ ]（如果你不喜欢，我建议你下载它如果你开发了linq的东西，它是必须的.​​.....，但你可以编写一个简单的转储器或检查VS中的排序列表。如您所见，甚至没有定义类，所有对象都是内联的。如果将构造函数参数更改为在所有对象中不常见的属性，则无法工作 - 在这种情况下，您必须决定并向比较器添加逻辑，以便比较不存在的属性。但您可以使用此示例来实现满足您需求的比较器。

This sample will run directly in LinqPad[^] (I suggest you download it if you don''t have it already, it is a must if you develop linq stuff...), but you can write a simple dumper or inspect the sorted list in VS. As you can see, there is not even a class defined, all objects are inline. Won''t work if you change the constructor parameter to a property that''s not common in all objects - in such case you have to decide and add logic to the comparer how to compare nonexistent properties. But you can use this sample to implement a comparer for your needs.

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