try { int a = 0; int b = 5 / a; }
catch (System.Exception ex) { Trace.Warn("zzl", "calling b=5/a", ex); }

public void PRocessRequest (HttpContext context) {
         context.Response.ContentTyPE = "text/plain";
         string ispostback = context.Request["ispostBack"];
         string value = "0";
         if (ispostback == "true") {
              value=context.Request["num_01"];
              int valueinint = int.Parse(value);
              valueInint++;
              value = valueInint.ToString();
         }

         string filepath = context.Server.MapPath("addTest.htm");
         string content = System.IO.File.ReadAllText(filepath);
         content = content.Replace("@value",value);
         context.Response.WrITe(content);
     }

<form action="addTest.ashx" method="post">
        <input type="hidden" name="ispostBack" value="true" />
        <input type="hidden" name="num_01" value="@value" />
    <div>@value
    </div>
        <input type="submit" name="" value="addOne" />
    </form>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class vivideo_test_变量1 : System.Web.UI.Page
{
    private int i = 0;
    private static int j = 0;
    protected void Page_Load(object sender, Eventargs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        //i++;
        //Label1.Text = i.ToString();

        j++;
        Label1.Text = j.ToString();
    }
}