如何动态更改字典中键的类型? [英] How to dynamically change type of a key in a dictionary?

问题描述

大家好！

我需要一个小问题的帮助.我正在列出具有几个属性的客户列表，并且我想创建一个使用字典来遍历所有客户的搜索功能，但是该字典的键必须动态更改， 所以我可以使用多个属性作为搜索参数.

I need help with a small problem. I am making a list of customers that have a couple properties, and i would like to make a search function that will use dictionary to loop through all customers, but the key of that dictionary has to be dynamically changed, so i can use multiple properties as a search parameter.

这是我的课程:

public class Customer
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Salary { get; set; }
    }

我在这里吸引客户并将其添加到列表中:

Here i am making customers and adding them to the list:

Customer c1 = new Customer() { ID = 1, Name = "Mike", Salary = 5000 };
Customer c2 = new Customer() { ID = 2, Name = "John", Salary = 6500 };
Customer c3 = new Customer() { ID = 3, Name = "Steve", Salary = 3500 };

List<Customer> listOfCustomers = new List<Customer>();
listOfCustomers.Add(c1);
listOfCustomers.Add(c2);
listOfCustomers.Add(c3);

现在，我正在制作字典并使用foreach遍历它:

Now, i am making a dictionary and looping through it with foreach:

Dictionary<object, Customer> searchCustomers = listOfCustomers.ToDictionary(c => (object)c.ID, c => c);

foreach (KeyValuePair<object,Customer> customer in searchCustomers)
{
     Customer x = customer.Value;

     Console.WriteLine("Customer ID = {0}, Name = {1}, Salary = {2}",
                    x.ID, x.Name, x.Salary);
}

字典的值是Customer类型的，因此它将返回该实例的所有属性.

Value of the dictionary is of type Customer, so it will return all properties of that instance.

由于我将字典的键作为对象，所以我始终可以:

Since i made the key of dictionary as object, i can always do:

c => (object)c.Name

或

c => (object)c.Salary

它将根据该参数进行搜索.

And it will search by that parameter.

但是，我必须在代码中手动更改它.我有什么办法可以动态更改它，以便客户端可以自己选择要搜索的参数?

BUT, i have to change that manually in code. Is there any way that i can change this dynamically, so that the client can choose the parameter for search by himself?

这是我到目前为止尝试过的:

This is what i tried so far:

string key = "Name";

和

c => (object)c.key

所以我可以动态更改字符串，但是那样行不通.

so i could change string dynamically, but it does not work that way.

我也尝试过使用反射:

Type T = Type.GetType("Exercise.Customer");

PropertyInfo[] properties = T.GetProperties();

List<string> listOfProperties = new List<string>();

foreach (PropertyInfo property in properties)
{
    listOfProperties.Add(property.Name);
}

但是结果基本上是一样的，因为我仍然会得到一个字符串值，就像我使用

But the outcome is basically the same, since i will still get a string value, just like when i did with 

string key = "Name";

c => (object)c.key

c => (object)c.key

我最后尝试做的是列出属性类型列表:

The last thing i tried is making a list of property types:

List<Type> listOfProperties = new List<Type>();

foreach (PropertyInfo property in properties)
{
    listOfProperties.Add(property.PropertyType);
}

我打印了该列表，它确实显示了Customer类中的所有类型的属性.

I printed the list and it does show all types of properties in class Customer.

因此，我尝试将字典的键设置为属性类型列表:

So, i tried to set the key of the dictionary as list of property types:

Dictionary<List<Type>, Customer> searchCustomers = listOfCustomers.ToDictionary(???);

但是我不知道这是否有可能，以及如何在此处设置键和值参数.

But i have no idea is this even possible, and how to set the key and value parameters here.

请帮助！ :)

推荐答案

您可以创建扩展方法或常规方法，以委托作为输入，并留在调用方上以指定要分配的属性用于字典中的键:

You can create an extension method or a normal method which takes a delegate as input and leave on the caller to specify which property to use for Key in dictionary :

public static Dictionary<TKey, Customer> ToDictionary<TKey>(Func<Customer,TKey> key,List<Customer> customers)
{

    var dict = new Dictionary<TKey, Customer>();
    foreach(var item in customers)
    {
       dict.Add(key.Invoke(item),item);
    }

    return dict;
}

您可以像现在这样调用它，我现在在Customer类上对其进行了定义，因此您可以在其中定义方法:

and you can call it like, i defined it on Customer class for now, so it is up to you where you want to define the method:

Customer.ToDictionary(x=>x.ID, listOfCustomers);

希望有帮助！

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