Ajax简单应用,检测用户名是否存在_[AJAX教程]

客户端页面index.html

onclick="javascript：HelloWorld();" />

服务器端功能页面Check.aspx

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class Check : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string str = "select Count(*) from Table where Name=" + Request.QueryString["id"].ToString() + "";
SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=Database;Integrated Security=True");
conn.Open();
SqlCommand cmd = new SqlCommand(str, conn);
int i = (int)cmd.ExecuteScalar();
conn.Close();
Response.Write(i);
}
}