using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<string, string> data = new Dictionary<string, string>();
            data.Add("aa", "11");
            data.Add("bb", "22");
            string[] keys = new string[data.Keys.Count];
            data.Keys.CopyTo(keys, 0);
            foreach (var key in keys)
            {
                data[key] = "55";
            }
            foreach (var key in data.Keys)//裡面的操作都會報錯，無法操作，所以採用上面先儲存KEYS，然後再處理的方式。
            {
                //data.Add("cc", "33");
                //data[key] = "33";
                //data.Remove("aa");
            }
            Console.ReadKey();
        }
    }
}