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));
        }
    }
}

除了内部（通过API管理），我想阻止向此词典添加新元素。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的内容必须可公开访问，因此只需翻转访问修饰符

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是您可以编辑的实际支持词典。

或者甚至更好，公开你想通过你的类可用的方法（它作为代理），你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>();

或另外使用ReadOnlyDictionary包装器以防止转回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));
    }
}

阻止添加到公共词典

2 个答案: