using System;
using System.Collections;
class ForeachApp
{
    public static void Main()
    {
        IDictionary environment = Environment.GetEnvironmentVariables();
        
      
        Console.WriteLine("text");
        
        foreach (string environmentKey in environment.Keys)
        {
            
            Console.WriteLine("{0}\t=\t{1}", environmentKey, environment[environmentKey].ToString());
        }
    }
}
請問紅色部份字體是什麼意思？?system.collections命名空間有什麼什麼類,什麼時候需用到呢？