菜鸟求大神，一个简单的注册网站，总是出现无法将int类型转换成string的错误，数据库Age字段是Int
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

public partial class Register : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string userid = this.lbUserID.Text.Trim();
        string password = this.lbPassword.Value.Trim();
        string password1 = this.lbpassword1.Value.Trim();
        string xb = this.tbXB.Text.Trim();
        int age = int.Parse(this.tbAge.Text.ToString());
        string tel = this.tbTel.Text.Trim();
        string email = this.tbEmail.Text.Trim();
        if (password == password1)
        {
            AddUser(userid, password,xb,age,tel,email);
            Response.Redirect("Viewer.aspx");
        }
    }
    private void AddUser(string userid, string password,string xb,int age,string tel,string email)
    {
        SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\Usermanagement.mdf;Integrated Security=True;User Instance=True");
        SqlCommand cmd = con.CreateCommand();
        con.Open();
        cmd.CommandText = "insert into [UserInfo](UserID,Password,XB,Age,Tel,[E-mail])values(@un,@pw,@xb,@age,@tel,@email)";
        cmd.Parameters.AddWithValue("un", userid); // 将username 赋值给命令行的"un” 
        cmd.Parameters.AddWithValue("pw", password); // 将Password 赋值给命令行的"pw”,以下类似
        cmd.Parameters.AddWithValue("xb", xb);
        cmd.Parameters.AddWithValue("age", age);
        cmd.Parameters.AddWithValue("tel", tel);
        cmd.Parameters.AddWithValue("email",email);
        cmd.ExecuteNonQuery();                     // 执行数据库命令
        lbUserID.Text = "";                             /