看看这个n*n乘法表输出问什么不能输出,该如何处理

看看这个n*n乘法表输出问什么不能输出
[code=C#][/code]using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class _2 : System.Web.UI.Page
{
   
  protected void mul(int x)
  {
  int i, j;
  TableRow tr;
  TableCell tc;
  for ( i = 1; i <= x ; i++)
  {
  tr = new TableRow();
  for ( j = 1; j <= i; j++)
  {
  tc = new TableCell();
  tc.BorderWidth = 1;
  tc.Text = i + "*" + j + "=" + (i * j);
  tr.Cells.Add(tc);
  }
  Table1.Rows.Add(tr);
  }
  }
  protected void Page_Load(object sender, EventArgs e)
  {
  mul(9);
  }
  protected void Button1_Click(object sender, EventArgs e)
  {
  Table1.Rows.Clear();

  int a = Convert.ToInt32(TextBox1.Text);
  mul(a); 
   
  }
}
用的vs2008，web标准控件，可以显示9*9的，初始化正确，问什么不能根据输入数值显示

------解决方案--------------------------------------------------------

C# code

protected void Page_Load(object sender, EventArgs e)  {            if (!IsPostBack)            {                mul(9);            }  }