杀死/清除文本直到缓冲区结束的替代方法是什么？(What is the alternative to kill/clear text till the end of buffer?)

 这是因为当你点击按钮时，它不会直接进入Button1_Click事件，它会从顶部到底部，因此它首先加载Page_Load然后它会进入事件，因此您应该放置一个支票 
 
      if (IsPostBack && Session["MyVar"] != null)
        {
            varcheck(Session["MyVar"].ToString());
        }
 
 如果Session["MyVar"]不为null因为它在第一次postback时将为空，因此它不会抛出异常 
 
 编辑1 
 
 如果不想使用会话，则可以使用静态变量来存储数据 
 
    public static string MyVar;
    protected void Page_Load(object sender, EventArgs e)
    {


    if (!string.IsNullOrWhiteSpace(MyVar))
    {
        varcheck(MyVar);
    }
}
 
 你可以点击设置值 
 
protected void Button1_Click(object sender, EventArgs e)
    {
      if (string.IsNullOrWhiteSpace(MyVar))
      {
        MyVar= "Return this on postback";
        varcheck(MyVar);

      }

    }

this is because when you click on button it does not go directly to Button1_Click Event it goes from top to bottom so it loads the Page_Load first then it goes to the event so you should place a check 
 
      if (IsPostBack && Session["MyVar"] != null)
        {
            varcheck(Session["MyVar"].ToString());
        }
 
that if Session["MyVar"] is not null because it will be null in first postback to it will not throw exception
 
Edit 1
 
if dont want to use session you can use static variable to store data
 
    public static string MyVar;
    protected void Page_Load(object sender, EventArgs e)
    {


    if (!string.IsNullOrWhiteSpace(MyVar))
    {
        varcheck(MyVar);
    }
}
 
and you can set value on click like
 
protected void Button1_Click(object sender, EventArgs e)
    {
      if (string.IsNullOrWhiteSpace(MyVar))
      {
        MyVar= "Return this on postback";
        varcheck(MyVar);

      }

    }