C# 中的通用函数，它采用随机类列表和某些属性名称的数组作为参数

Question

I want to write a generic function that can print any certain property values. One parameter is a list of random class, another parameter is an array of certain class property names. The function is able to print given property value of each element in the list. Assuming I have two classes of two lists of them:

class visitor {
    public string name;
    public string age;
    public string address;
    public string nationality;
}

class menu {
    public string dish;
    public double prise;
    public string chef;
    public bool isForVIP;
}

List<visitor> visitorList, List<menu> menuList

Now I want only the function void GenericOutput(List<AnyObject> objList,string[] certainProperties) to output a part of each class properties. For example:

GenericOutput(visitorList,new string[]{ "name","age" });
GenericOutput(menuList,new string[]{ "dish","double","isForVIP" });

How can I design the function in C#? Could some help me?

Answer 1

By using reflection, you can:

1. Create a generic method.
2. Get the run time type from the generic type argument.
3. Get information about the properties of the type.
4. Extract the values from each object of the type.

Example:

public void GenericOutput<T>(List<T> objects, string[] propertyNames)
{
    // Get the generic type.
    Type type = typeof(T);

    // Get the requested properties of the type.
    var propertyInfos = propertyNames.Select(pn => type.GetProperty(pn));
        
    foreach (var obj in objects)
    {
        foreach (var propertyInfo in propertyInfos)
        {
            // For each given object, iterate the properties of 
            // the type and get the property value from the object.
            var value = propertyInfo.GetValue(obj);
            // Print or do whatever with the value...
            Console.WriteLine(value);
        }
    }
}

Answer 2

Try this,

class Program
    {
        static void Main(string[] args)
        {
            var visitors = new List<Visitor>() 
            { 
                new Visitor(){Name="Visitor1",Age="30",Address="adress1",Nationality="Nationality1"},
                new Visitor(){Name="Visitor2",Age="20",Address="adress2",Nationality="Nationality2"},
                new Visitor(){Name="Visitor3",Age="10",Address="adress3",Nationality="Nationality3"},
                new Visitor(){Name="Visitor4",Age="50",Address="adress4",Nationality="Nationality4"},
                new Visitor(){Name="Visitor5",Age="90",Address="adress5",Nationality="Nationality5"},

            };
            GenericOutput(visitors, new string[] { "Name", "Age", "Address" });
            Console.ReadKey();
        }
        private static void GenericOutput<T>(List<T> obj, string[] properties)
        {
            var t = typeof(T);
            foreach (var item in obj)
            {
                foreach (var propName in properties)
                {
                    var propValue = (t.GetProperty(propName).GetValue(item) ?? string.Empty).ToString();
                    Console.WriteLine($"{propName}:{propValue}");
                }
                Console.WriteLine("-----------");
            }
        }
    }
    class Visitor
    {
        public string Name { get; set; }
        public string Age { get; set; }
        public string Address { get; set; }
        public string Nationality { get; set; }
    }

Result: