防止添加到公共字典

Question

我在公共课堂上有一个公共字典如下:

namespace ApiAssembly
{
    public static class TypeStore
    {
        /// <summary>
        /// Initializes static members of the <see cref="TypeStore"/> class.
        /// </summary>
        static TypeStore()
        {
            Store = new Dictionary<string, Type>();
        }

        /// <summary>
        /// Gets the store.
        /// </summary>
        public static Dictionary<string, Type> Store { get; }

        public void AddTypes()
        {
            // This should be allowed
            TypeStore.Store.Add("object", typeof(object));
        }
    }
}

我想阻止在内部添加新元素(通过API管理).实现这一目标的最佳方法是什么？

namespace ClientAssembly
{
    using ApiAssembly;

    public class Client
    {
        public void AddTypes()
        {
            // How to prevent this call?
            TypeStore.Store.Add("object", typeof(object));
        }
    }
}

Dictionnary的内容必须是可公开访问的,因此只需翻转访问修饰符就不是一种选择

Answer 1

您应该将实际存储字典与您用于外部世界的字典分开.一个简单的方法是:

private static Dictionary<string, Type> Storage { get; } = new Dictionary<string, Type>();

public static ReadOnlyDictionary<string, Type> Store 
              => new ReadOnlyDictionary<string, Type>(Storage);

Storage您可以编辑的实际支持字典在哪里.

或者甚至更好,通过您的类(它充当代理)公开您想要的方法,在这里您永远不会授予外部类访问字典本身的权限.

Answer 2

将其公开为:

IReadOnlyDictionary<string, Type> dictionary = new Dictionary<string, Type>();

或者另外使用ReadOnlyDictionary包装纸以防止回流Dictionary.

完整示例:

public static class TypeStore
{
    private static Dictionary<string, Type> store;

    private static ReadOnlyDictionary<string, Type> storeReadOnly ;

    /// <summary>
    /// Initializes static members of the <see cref="TypeStore"/> class.
    /// </summary>
    static TypeStore()
    {
        store = new Dictionary<string, Type>();
        storeReadOnly = new ReadOnlyDictionary<string, Type>(store);
    }

    /// <summary>
    /// Gets the store.
    /// </summary>
    public static IReadOnlyDictionary<string, Type> Store => storeReadOnly;

    public static void AddTypes()
    {
        // This should be allowed
        TypeStore.store.Add("object", typeof(object));
    }
}