系统对象的使用——Cookie，ViewState，Session，Application

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7.8 磅
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2

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/* Style Definitions */
table.MsoNormalTable
{mso-style-name:普通表格;
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin:0cm;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.5pt;
mso-bidi-font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;
mso-hansi-font-family:Calibri;
mso-hansi-theme-font:minor-latin;
mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;
mso-font-kerning:1.0pt;}

Cookie

//将数据保存到Cookie
       
//Cookie是一个字典
        //如果没有指定Cookie的保存时间，则这个Cookie是临时Cookie
        //临时Cookie只要浏览器一关闭，就取消
       
//Response.Cookies["account"].Value = txt1.Text;

//如果指定了Cookie的保存时间，这个Cookie就叫持久Cookie
        Response.Cookies["account"].Value =
txt1.Text;
       
Response.Cookies["account"].Expires = DateTime.Now.AddMinutes(1);

//Response.Cookies["account"].Expires = DateTime.Now.AddMinutes(-1);

if
(Request.Cookies["account"] != null)
        {
           
lab1.Text = Request.Cookies["account"].Value;
        }

ViewState

利用ViewState保持页面状态_页面状态对象

protectedvoid
btn3_Click(object sender, EventArgs
e)

{

a =
10;

b =
20;

//ViewState是一个字典，键值对

//ViewState用于本页面回发时保持状态

ViewState["a"] = a;

ViewState["b"] = b;

}

protectedvoid
btn4_Click(object sender, EventArgs
e)

{

a = Convert.ToInt32(ViewState["a"]);

b = Convert.ToInt32(ViewState["b"]);

c = a
+ b;

lab2.Text = c.ToString();

}

Session

Session["username"] = txt1.Text;

if
(Session["username"] != null)

{

lab1.Text = Session["username"].ToString();

}

Application公共对象

//因为Application对象时公共对象

//当多个用户同时修改Application对象时，可能会引发不可预知的问题

//并发

Application.Lock();//锁定对象

//Application.Add("account",
txt1.Text);

Application["account"] =
txt1.Text;

//...

Application.UnLock();//解锁对象

if (Application["account"] != null)

{

lab1.Text = Application["account"].ToString();

}

//ViewState是一个字典，键值对
        //ViewState用于本页面回发时保持状态
        ViewState["a"] = a;
        ViewState["b"] = b;