高手来看看,关于ajax三级联动无刷新,为什么要把页面关掉重新打开下拉列表的项才能重新绑定？

Question

用ajax实现的局部刷新,当点击按钮往数据库中添加下拉列表的项，数据库中数据已经更新，但是下拉列表中的项没有更新，把页面关掉再打开却得到了更新，请问是什么原因？

Answer 1

你的AJAX是怎么写的是关键。
你这样问太简单了，没有办法回答

Answer 2

点button后,在把数据bind()
不过你问的比较笼统了，

Answer 3

代码比较多，望各位大虾包含，以下为前台代码，关于xmlhttprequest对象如何获得小弟在此就只考虑ie浏览器
                            var xmlHttp = false;

//创建XMLHttpRequest对象函数
function GetXMLHttpRequest()
{
// 由于 XMLHttpRequest 对象在各个浏览器中实现机制不同,所以要综合考虑
    var xmlHttp = false;
    //如果是IE浏览器
    if(window.ActiveXObject)
    {
    try 
    {
    xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
    } 
    catch (e) 
    {
    try 
    {
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } 
    catch (e2) 
    {
    xmlHttp = false;
    }
    }     
    }
    return xmlHttp;
}

function getSecondCategory()
{
var RootCategory = document.getElementById("<%=RootCategory.ClientID%>");
var hidden=document.getElementById("<%=HiddenArea.ClientID%>");
hidden.value="";
hidden.value=RootCategory.options[RootCategory.selectedIndex].value;
//if (RootCategory.Items == null)
//return;
                xmlHttp = GetXMLHttpRequest();
// 构造将XMLHttpRequest对象将请求的服务器端的URL字符串
//alert(RootCategory.options[RootCategory.selectedIndex].value);
var url = "GetSecondCategory.aspx?CategoryID="+RootCategory.options[RootCategory.selectedIndex].value;
// 建立与服务器端的连接
xmlHttp.open("GET", url, true);
// 设置回调函数
xmlHttp.onreadystatechange = callBack_getSecondCategory;
// 发送请求
xmlHttp.send(null);
}

function callBack_getSecondCategory()
{
    var f=document.getElementById("<%=SecondCategory.ClientID%>");
    var lbl=document.getElementById("lbl1");
    var lbl2=document.getElementById("lbl2");
    if (4 == xmlHttp.readyState) 
{
    if(xmlHttp.status==200)
{
var list=xmlHttp.responseText;
var classList=list.split("|");
lbl2.innerHTML=classList.length;
f.options.length=1;
for(var i=0;i<classList.length;i++)
{
var tmp=classList[i].split(",");
f.add(new Option(tmp[1],tmp[0]));
}
}
else
{
alert("您所请求的页面有异常。");
}
}
                else
{
//    alert("else");
    //lbl.innerHTML ="yyy"; 
}
}

    function getThirdCategory()
{
var SecondCategory = document.getElementById("<%=SecondCategory.ClientID%>");
var hidden=document.getElementById("<%=HiddenArea.ClientID%>");
hidden.value="";
hidden.value=SecondCategory.options[SecondCategory.selectedIndex].value;
//if (RootCategory.Items == null)
//return;
                xmlHttp = GetXMLHttpRequest();
// 构造将XMLHttpRequest对象将请求的服务器端的URL字符串
var url = "GetSecondCategory.aspx?CategoryID="+SecondCategory.options[SecondCategory.selectedIndex].value;
// 建立与服务器端的连接
xmlHttp.open("GET", url, true);
// 设置回调函数
xmlHttp.onreadystatechange = callBack_getThirdCategory;
// 发送请求
xmlHttp.send(null);
}

function callBack_getThirdCategory()
{
    var f=document.getElementById("<%=ThirdCategory.ClientID%>");
    var lbl=document.getElementById("lbl2");
    if (4 == xmlHttp.readyState) 
{
    if(xmlHttp.status==200)
{
    lbl.innerHTML =xmlHttp.responseText;
var list=xmlHttp.responseText;
var classList=list.split("|");
f.options.length=1;
for(var i=0;i<classList.length;i++)
{
var tmp=classList[i].split(",");
f.add(new Option(tmp[1],tmp[0]));
}
}
else
{
alert("您所请求的页面有异常。");
}
}
                else
{
    lbl.innerHTML ="yyy"; 
}
}

function getParentCategoryName()
{
    var ThirdCategory=document.getElementById("<%=ThirdCategory.ClientID%>");
var hidden=document.getElementById("<%=HiddenArea.ClientID%>");
hidden.value="";
hidden.value=ThirdCategory.options[ThirdCategory.selectedIndex].value;     
}后台代码
    protected void Page_Load(object sender, EventArgs e)
    {
        Page.Title = "管理员-->商品类别";
        bindRootCategory();
        RootCategory.Items.Insert(0, new ListItem("请选择分类", "0"));
        //SecondCategory.Disabled = true;
        //ThirdCategory.Disabled = true;
        this.btnDelete.Attributes.Add("onclick", "return confirm('您确定要删除吗？')");
    }    protected void Page_PreInit(object sender, EventArgs e)
    {
        Page.Theme = System.Configuration.ConfigurationManager.AppSettings["Theme"];
    }    protected void bindRootCategory()
    {
        using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ToString()))
        {
            SqlCommand cmd = new SqlCommand("select CategoryID,CategoryName from Category where ParentCategoryID=0", con);
            try
            {
                con.Open();
                RootCategory.DataSource = cmd.ExecuteReader();
                RootCategory.DataTextField = "CategoryName";
                RootCategory.DataValueField = "CategoryID";
                RootCategory.DataBind();
            }
            catch (Exception)
            {
                Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "yy", "<script>alert('系统错误!')</script>");
            }
        }
    }
    protected void btnAdd_Click(object sender, EventArgs e)
    {
        //lblMessage.Text = HiddenArea.Value;
        //Response.Write(RootCategory.SelectedIndex);
        using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ToString()))
        {
            SqlCommand cmd = new SqlCommand("insert into Category(ParentCategoryID,CategoryName) values(@ParentCategoryID,@CategoryName)", con);
            cmd.Parameters.AddWithValue("@CategoryName", txtNewCategoryName.Text.Trim());
            cmd.Parameters.AddWithValue("@ParentCategoryID",HiddenArea.Value);
            try
            {
                con.Open();
                cmd.ExecuteNonQuery();
                Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "xx", "<script>alert('操作成功!')</script>");
            }
            catch (Exception ex)
            {
                Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "yy", ex.Message);
            }
        }
        Server.Transfer("Category.aspx");
    }    protected void btnDelete_Click(object sender, EventArgs e)
    {
        lblMessage.Text = String.Empty;
        using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ToString()))
        {
            SqlCommand cmd = new SqlCommand("delete from Category where CategoryID=@CategoryID", con);
            cmd.Parameters.AddWithValue("@CategoryID", HiddenArea.Value);
            try
            {
                con.Open();
                cmd.ExecuteNonQuery();
                lblMessage.Text = "删除成功！";
            }
            catch(Exception ex)
            {
                lblMessage.Text = ex.Message;
            }
        }
    }

Answer 4

服务器处理页面GetSecondCategory.aspx.cs
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Clear();
        //System.Threading.Thread.Sleep(1000);
        String SecondCategory = getSecondCategory();        // 发送验证结果
        //    Response.Clear();
        //    Response.ContentType = "text/xml";
        Response.ContentType = "text/html";
        Response.Write(SecondCategory.ToString());
        Response.Flush();
        Response.End();
    }    protected String getSecondCategory()
    {
        DataSet ds = new DataSet();
        DataTable table = new DataTable();
        table.Columns.Add(new DataColumn("CategoryID", typeof(String)));
        table.Columns.Add(new DataColumn("CategoryName", typeof(String)));
        String CategoryName=String.Empty;
        using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ToString()))
        {
            SqlCommand cmd = new SqlCommand("select CategoryID,CategoryName from Category where ParentCategoryID=@CategoryID", con);
            cmd.Parameters.AddWithValue("@CategoryID", Request.QueryString["CategoryID"]);
            try
            {
                con.Open();
                SqlDataAdapter adp = new SqlDataAdapter(cmd);
                adp.Fill(ds);
                for (int i = 0; i < ds.Tables[0].Rows.Count;i++ )
                {
                    if (i == ds.Tables[0].Rows.Count - 1)
                    {
                        CategoryName += ds.Tables[0].Rows[i]["CategoryID"].ToString() + "," + ds.Tables[0].Rows[i]["CategoryName"].ToString();
                    }
                    else
                    {
                        CategoryName += ds.Tables[0].Rows[i]["CategoryID"].ToString() + "," + ds.Tables[0].Rows[i]["CategoryName"].ToString() + "|";
                    }
                }
            }
            catch(Exception ex)
            {
                Response.Write(ex.Message);
            }
        }
        return CategoryName;
    }