单例作为全局变量的一种方式

本文内容：利用单例的方式实现一个作为全局变量的简单方法。用代码说明，比较清晰一点。

UserPool.cs

class UserPool
    {
publicstaticreadonly UserPool GlobalUserPool =new UserPool();
private Hashtable ht =new Hashtable();

private UserPool()
        {
        }
publicvoid Add(string key, UserInformation userInfor)
        {
lock (ht.SyncRoot)
            {
                ht[key] = userInfor;
            }
        }

publicvoid Remove(string key)
        {
if (ht.ContainsKey(key))
            {
lock (ht.SyncRoot)
                {
if (ht.ContainsKey(key))
                    {
                        ht.Remove(key);
                    }
                }
            }
        }

public UserInformation GetUserInfo(string key)
        {
if (ht.ContainsKey(key))
            {
lock (ht.SyncRoot)
                {
if (ht.ContainsKey(key))
                    {
return ht[key] as UserInformation;
                    }
else
                    {
returnnull;
                    }
                }
            }
else
            {
returnnull;
            }
        }

publicbool ContainsKey(string key)
        {
return ht.ContainsKey(key);
        }
    }

UserInformation.cs

class UserInformation
    {
publicstring[] UserFriends { get; set; }
publicstring KeyGuid { get; set; }
publicstring Name { get; set; }
    }