C#实例之简单聊天室（状态管理）

protected void Button1_Click(object sender, EventArgs e)
        {
            Application.Lock();
            int intUserNum;
            string user;
            string[] users;
            string strUserName;
            intUserNum = Convert.ToInt32(Application["userNum"]);
            if (intUserNum > 20)
            {
                Response.Write("在线人数超过20人，不能登录了！");
                Response.Redirect("Default.aspx");
            }
            else {
                user = Application["user"].ToString();
                users = user.Split(‘,‘);
                strUserName = TextBox1.Text.Trim();
                for (int i = 0; i < intUserNum; i++) {
                    if (users[i] == strUserName)
                    {
                        Response.Redirect("Default.aspx?value=1");
                    }
                }
                if (users == null)
                    Application["user"] = strUserName;
                else
                    Application["user"] += "," + strUserName;
                    intUserNum += 1;
                    Application["userNum"] = intUserNum.ToString();
                    Session["user"] = strUserName;
                    Application.UnLock();
                    Response.Redirect("main.aspx"); ;        
            }
        }

public partial class Left : System.Web.UI.Page
    {
        private ArrayList ItemList = new ArrayList();
        protected void Page_Load(object sender, EventArgs e)
        {
            Application.Lock();
            if (Session["user"] == null)
                Response.Redirect("Default.aspx");
            else
                Label1.Text = Session["user"].ToString();
            int userCount = int.Parse(Application["userNum"].ToString());
            Label2.Text = userCount.ToString();
            string user = Application["user"].ToString();
            string[] users = user.Split(‘,‘);
            for (int i = (userCount-1); i >= 0; i--) {
                ItemList.Add(users[i]);
            }
            ListBox1.DataSource = ItemList;
            ListBox1.DataBind();
            Application.UnLock();
        }
    }

protected void Page_Load(object sender, EventArgs e)
        {
            Application.Lock();
            if (!IsPostBack) {
                string chat=Application["chats"].ToString();
                int chatNum=int.Parse(Application["current"].ToString()) ;
                string[] chats = chat.Split(‘,‘);
                for (int i = chatNum - 1; i >= 0; i--)
                {
                    if(chatNum==0)
                        TextBox1.Text=chats[i];
                    else
                        TextBox1.Text=TextBox1.Text+"\n"+chats[i];
                }
            }
            Application.UnLock();
        }

public partial class bottom : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Application.Lock();
            string userName = Application["user"].ToString();
            string[] users = userName.Split(‘,‘);
            DropDownList1.DataSource = users;
            DropDownList1.DataBind();
            Application.UnLock();
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            Application.Lock();
            int current = int.Parse(Application["current"].ToString());
            string liaotian = Session["user"] + "对" + DropDownList1.SelectedValue.ToString() + "说：" + TextBox1.Text.Trim() + DateTime.Now.ToString();
            if (current == 0 || current > 40)
            {
                current = 0;
                Application["chats"] = liaotian;
            }else{
                Application["chats"] +=","+ liaotian;
            }
            current += 1;
            Application["current"] = (object)current;
            Application.UnLock();
        }
    }

<div>
    <iframe id="ifraLeft" name="ifraLeft" src="Left.aspx" 
        style="width:200px;height:500px;float:left;margin-left:10px;margin-top:10px;background-color:grey;border:2px solid #000000"></iframe>  
    <iframe id="ifraRight" name="ifraRight" src="Right.aspx" 
    style="width:700px;height:500px;float:left;margin-top:10px;background-color:#000000;border:2px solid #000000;"></iframe>  
    <iframe id="ifrabottom" name="ifrabottom" src="bottom.aspx" 
    style="width:900px;height:50px;margin-left:10px;margin-top:10px;background-color:red;border:2px solid #000000;"></iframe>  
</div>