C# - 如何在类上实现IEnumerator

Question

如何在这个类上实现IEnumerator,以便我可以在foreach循环中使用它.

public class Items
    {
        private Dictionary<string, Configuration> _items = new Dictionary<string, Configuration>();

        public Configuration this[string element]
        {
            get
            {

                if (_items.ContainsKey(element))
                {
                    return _items[element];
                }
                else
                {
                    return null;
                }
            }

            set
            {
                _items[element] = value;
            }
        }
   }

在此示例中,Configuration是一个具有很少属性的简单类.

Answer 1

只是一个实现类型安全的示例,IEnumerable而不是IEnumerator您可以在foreach循环中使用的示例.

   public class Items : IEnumerable<Configuration>
    {
        private Dictionary<string, Configuration> _items = new Dictionary<string, Configuration>();


        public void Add(string element, Configuration config) {
            _items[element] = config;
        }

        public Configuration this[string element]
        {
            get
            {

                if (_items.ContainsKey(element))
                {
                    return _items[element];
                }
                else
                {
                    return null;
                }
            }

            set
            {
                _items[element] = value;
            }
        }

        public IEnumerator<Configuration> GetEnumerator()
        {
            return _items.Values.GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return _items.Values.GetEnumerator();
        }
    }

问候.

Answer 2

你应该能够IEnumerator像这样实现:

public class Items : IEnumerator<KeyValuePair<string, Configuration>>  
{        
    private Dictionary<string, Configuration> _items = new Dictionary<string, Configuration>();        
    public Configuration this[string element]       
    {            
        get
        {
            if (_items.ContainsKey(element))
            {
                return _items[element];
            }
            else
            {
                return null;
            }
        }
        set
        {
             _items[element] = value;
        }
    }

    int current;
    public object Current
    {
        get { return _items.ElementAt(current); }
    }

    public bool MoveNext()
    {
        if (_items.Count == 0 || _items.Count <= current)
        {
            return false;
        }
        return true;
    }

    public void Reset()
    {
        current = 0;
    }

    public IEnumerator GetEnumerator()
    {
        return _items.GetEnumerator();
    }

    KeyValuePair<string, Configuration> IEnumerator<KeyValuePair<string, Configuration>>.Current
    {
        get { return _items.ElementAt(current); }
    }

    public void Dispose()
    {
        //Dispose here
    }
}

但正如已经指出的那样,你也可以实施IEnumerable.

Answer 3

您不需要实现IEnumerable或任何接口。为了能够在 a 中使用您的类foreach，您只需要使用以下签名向您的类添加一个实例方法：

IEnumerator GetEnumerator()