C# - 通过 public 属性使私有嵌套 class 可见

Question

我有以下无法编译的代码：

public class Outer
  {
    public Inner MyField = new Inner(); //error here: "field type is less accessible than field"
    private class Inner
    {
        public string Message = "Hello";
    }
  }

我必须能够像这样使用 class：

var MyObject = new Outer();
Console.WriteLine(MyObject.MyField.Message); //should output "Hello"

"Inner" 必须 ONLY 可以从 "Outer" 中实例化，所以这应该 NOT 被允许：

var MyObject = new Outer.Inner(); //I do not want users to be able to instantiate "Inner" directly

Answer 1

解决这个问题的典型方法是通过接口：

public class Outer
{
    public IInner Inner = new Inner();
    public interface IInner { ... }

    private class Inner: IInner { ... }
}

IInner无需嵌套，任意选择均可。

此模式的一个有趣变体是嵌套的 class 继承自外部 class。这是一个非常方便的代码结构，允许真正优雅的解决方案：

public abstract class Outer
{
     public static Outer GetOuter(...)
     {
         if (someConditionMet) return new InnerSpecialized1();
         return new InnerSpecialized2();
     } 

     private Outer() { ... } //avoids anyone extending Outer

     private class InnerSpecialized1: Outer { ... }
     private class InnerSpecialized2: Outer { ... }
}

Answer 2

您只需要公开字段的 getter 并在 class:

中构造实例

public class Outer
{
    public Outer()
    {
        MyField = new MyField();
    }
    public Inner MyField {get; private set;}
}

public class Inner
{        
    internal Inner()
    {
    }
    public string Message = "Hello";
}

C# - 通过 public 属性使私有嵌套 class 可见

C# - Make a private nested class visible through a public property

c#

class

static

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public

C# - 通过 public 属性 使私有嵌套 class 可见

C# - Make a private nested class visible through a public property

c#

class

static

private

public

C# - 通过 public 属性使私有嵌套 class 可见