Question

假设我有一个父类的对象，我无法更改 - 例如，ListBox的实例包含很长的参数列表。现在我创建一个子类：

class PlaylistBox : ListBox
{

    void CopySettingsFrom(ListBox In)
    {
         //...what now?
    }
}

问题 - 如何有效地从In对象到PlaylistBox的新对象进行浅层复制？

Answer 1

您可以使用反射

//Other Imports...
using System.Reflection;

public PlaylistBox(ListBox In)
{
    PropertyInfo[] properties = typeof(ListBox).GetProperties();

    foreach (PropertyInfo p in properties)
        if (p.CanRead && p.CanWrite)
            p.SetMethod.Invoke(this, new object[] { p.GetMethod.Invoke(In, null) });
}

对于.NET＆lt; 4.5，分别通过调用GetMethod和SetMethod方法来调用GetGetMethod()和GetSetMethod()属性。

Answer 2

这里有3个方法的例子，基于反射和AutoMapper以及解释：

internal class Program
    {
        private static void Main(string[] args)
        {
            Example1();
            Example2();
            Example3();
        }

        public static void Example1()
        {
            Console.WriteLine("This example shows using copy with reflection. Minus of this method - u have to implement FULL copy for each class or u will copy only references to object properties");

            //creating new parent class with some values
            var parentClass = new ParentClass
            {
                Property1 = "qqq",
                Property2 = 1,
                ObjectProperty = new SomeClassWithObjectProperty
                {
                    ObjectProperty = new SomeObjectClass {SomeProperty = "www"}
                }
            };

            //crating new child class and copy REFERENCES to properties
            var childClassReflection = new ChildClassReflection(parentClass);

            //changing properties of parent
            parentClass.Property1 = "rrr";
            parentClass.Property2 = 2;
            parentClass.ObjectProperty.ObjectProperty.SomeProperty = "eee";

            //we will get OLD values for VALUE types and OLD values for REFERENCE types
            //qqq 1 WWW
            Console.WriteLine(childClassReflection.Property1 + " " + childClassReflection.Property2 + " " + childClassReflection.ObjectProperty.ObjectProperty.SomeProperty);
        }

        public static void Example2()
        {
            Console.WriteLine();
            Console.WriteLine("This example shows using copy with reflection WITH FULL COPY");

            //creating new parent class with some values
            var parentClass = new ParentClass
            {
                Property1 = "qqq",
                Property2 = 1,
                ObjectProperty = new SomeClassWithObjectProperty
                {
                    ObjectProperty = new SomeObjectClass {SomeProperty = "www"}
                }
            };

            //crating new child class and copy REFERENCES to properties
            var childClassReflection = new ChildClassReflectionWithFullCopy(parentClass);

            //changing properties of parent
            parentClass.Property1 = "rrr";
            parentClass.Property2 = 2;
            parentClass.ObjectProperty.ObjectProperty.SomeProperty = "eee";

            //we will get OLD values for VALUE types and NEW values for REFERENCE types
            //qqq 1 eee
            Console.WriteLine(childClassReflection.Property1 + " " + childClassReflection.Property2 + " " + childClassReflection.ObjectProperty.ObjectProperty.SomeProperty);
        }

        public static void Example3()
        {
            //here i will show copy using AutoMapper
            Console.WriteLine();
            Console.WriteLine("This example shows using copy with AutoMapper");

            //creating new parent class with some values
            var parentClass = new ParentClass
            {
                Property1 = "qqq",
                Property2 = 1,
                ObjectProperty = new SomeClassWithObjectProperty
                {
                    ObjectProperty = new SomeObjectClass { SomeProperty = "www" }
                }
            };

            Mapper.Initialize(cfg => cfg.CreateMap<ParentClass, ChildClassAutoMapper>());           

            //crating new child class and copy REFERENCES to properties
            var childClassReflection = Mapper.Map<ChildClassAutoMapper>(parentClass);

            //changing properties of parent
            parentClass.Property1 = "rrr";
            parentClass.Property2 = 2;
            parentClass.ObjectProperty.ObjectProperty.SomeProperty = "eee";

            //we will get OLD values for VALUE types and OLD values for REFERENCE types
            //qqq 1 eee
            Console.WriteLine(childClassReflection.Property1 + " " + childClassReflection.Property2 + " " + childClassReflection.ObjectProperty.ObjectProperty.SomeProperty);
        }
    }

    public class ChildClassAutoMapper:ParentClass
    {       
    }

    public class ChildClassReflection : ParentClass
    {
        public ChildClassReflection(ParentClass parentClass)
        {
            foreach (var p in ParentProperties)
                p.SetMethod.Invoke(this, new[] {p.GetMethod.Invoke(parentClass, null)});
        }

        //do it only once for best performance
        private static PropertyInfo[] ParentProperties { get; } = typeof(ParentClass).GetProperties().Where(c => c.CanRead && c.CanWrite).ToArray();
    }

    public class ChildClassReflectionWithFullCopy : ParentClass
    {
        public ChildClassReflectionWithFullCopy(ParentClass parentClass)
        {
            var parentClassLocal = JsonConvert.DeserializeObject<ParentClass>(JsonConvert.SerializeObject(parentClass));
            foreach (var p in ParentProperties)
                p.SetMethod.Invoke(this, new[] {p.GetMethod.Invoke(parentClassLocal, null)});
        }

        //do it only once for best performance
        private static PropertyInfo[] ParentProperties { get; } = typeof(ParentClass).GetProperties().Where(c => c.CanRead && c.CanWrite).ToArray();
    }

    public class ParentClass
    {
        public string Property1 { get; set; }
        public int Property2 { get; set; }
        public SomeClassWithObjectProperty ObjectProperty { get; set; }
    }

    public class SomeClassWithObjectProperty
    {
        public SomeObjectClass ObjectProperty { get; set; }
    }

    public class SomeObjectClass
    {
        public string SomeProperty { get; set; }
    }

C＃将所有对象参数复制到子类对象

2 个答案: