var xmlHttp;

        function createXmlHttpRequest() {
            if (window.XMLHttpRequest) {
                xmlHttp = new XMLHttpRequest();

                if (xmlHttp.overrideMimeType) {
                    xmlHttp.overrideMimeType("text/xml");
                }
            }
            else if (window.ActiveXObject) {
                try {
                    xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
                }
                catch (e) {
                    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
            }
            if (!xmlHttp) {
                window.alert("你的浏览器不支持创建XMLhttpRequest对象");
            }
            return xmlHttp;
        }
function checkname(name) {
            createXmlHttpRequest();
            var url = "Customer/createcustomerAJAX.aspx?Name=" + name;
            xmlHttp.open("post", url, true);
            xmlHttp.onreadystatechange = CheckUserNameResult;
            xmlHttp.send(null);
        }

        function CheckUserNameResult() {
            if (xmlHttp.readyState == 4)//服务器响应状态
            {
                if (xmlHttp.status == 200)//代码执行状态
                {
                    if (xmlHttp.responseText == "true") {
                        document.getElementById("img_companyname").src = "../images/正确 .jpg";
                    }
                    else {
                        document.getElementById("imgflag").src = "../images/不能为空.jpg";
                        document.getElementById("Text1").style.display = true;
                    }
                }
            }
        }

checkcompanyname cu = new checkcompanyname();
            if (cu.checkcompany(Request.QueryString["Name"].ToString()))
            {
                Response.Write("false");

                Response.End();
            }
            else
            {
                Response.Write("true");

                Response.End();
            }

public bool checkcompany(string name)
        {
            string sql = "select * from customers where companyname='"+name+"'";
            SqlConnection con = new SqlConnection(SqlHelper.connectionString);
            con.Open();
            SqlCommand com = new SqlCommand(sql,con);
            SqlDataReader dr = com.ExecuteReader();
            if (dr.Read())
            {
                return true;
            }
            else
            {
                return false;
            }
        }