C#新手，看到书上一个 关于foreach的例子，无法运行

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace foreachApp
{
class Program
{
public static void Main()
{

        IDictionary environment = Environment.GetEnvironmentVariables();
        Console.WriteLine("环境变量名\t=\t环境变量值");
         //遍历environment中所有键值
        foreach (string environment in environment.Keys)
        {

            Console.WriteLine("{0}\t=\t{1}",environmentKey,environment [environmentKey].ToString());
        }
    }
}

}
大家帮忙看看哪里错误了，多谢

IDictionary environment = Environment.GetEnvironmentVariables();
Console.WriteLine("环境变量名\t=\t环境变量值");
//遍历environment中所有键值
foreach (string key in environment.Keys)
{

            Console.WriteLine("{0}\t=\t{1}", key, environment[key].ToString());
        }

添加 using System.Collections;

给你个完整的代码
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
class Program
{
static void Main(string[] args)
{
IDictionary environment = Environment.GetEnvironmentVariables();
Console.WriteLine("环境变量名\t=\t环境变量值");
//遍历environment中所有键值
foreach (DictionaryEntry de in environment)
{

            Console.WriteLine("{0}\t=\t{1}", de.Key, de.Value);
        }
    }
}

}

代码没问题，可以执行
完整代码：

 using System;
using System.Collections;

class Sample 
{
    public static void Main() 
    {
    Console.WriteLine();
    Console.WriteLine("GetEnvironmentVariables: ");
    IDictionary environmentVariables = Environment.GetEnvironmentVariables();
    foreach (DictionaryEntry de in environmentVariables)
        {
        Console.WriteLine("  {0} = {1}", de.Key, de.Value);
        }
    }
}