两个dropdownlist 的 postback 都发生了！bug还是viewstate 问题？
下面是测试网页，
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList2.Items.Clear();
DropDownList2.Items.Add(new ListItem("list2 item1"));
DropDownList2.Items.Add(new ListItem("list2 item2"));
}
protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList3.Items.Clear();
DropDownList3.Items.Add(new ListItem("list3 item1"));
DropDownList3.Items.Add(new ListItem("list3 item2"));
}
protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
{
Server.Transfer("htmlpage.htm"); // 建一个空网页即可
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true">
<asp:ListItem>list1 item1</asp:ListItem>
<asp:ListItem>list1 item2</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList3_SelectedIndexChanged">
</asp:DropDownList></div>
</form>
</body>
</html>
测试方法：依次选dropdownlist, dropdownlist2 和 dropdownlist3，你会自动转到下一个html页，这时候点 IE 工具栏中的后退按钮，回到选择页，再选dropdownlist1中的一项，这时候你会马上重新转到html页。
跟踪网页的执行你会发现第二次选dropdownlist1的时候,dropdownlist1的postback event发生了，但是同时dropdownlist3的postback event也发生了，可是实际上这个postback是list1发生的，和list3无关的，至少在client端时这样的。
.net 2.0, 1.1都测试了，一样地结果。
不知道这算是bug，还是viewstate的问题(by design?)。
<%@ Page Language="C#" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { 
DropDownList2.Items.Clear(); DropDownList2.Items.Add(new ListItem("list2 item1")); DropDownList2.Items.Add(new ListItem("list2 item2")); } protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e) { DropDownList3.Items.Clear(); DropDownList3.Items.Add(new ListItem("list3 item1")); DropDownList3.Items.Add(new ListItem("list3 item2")); } protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e) { Server.Transfer("htmlpage.htm"); // 建一个空网页即可 } </script> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title>Untitled Page</title> </head> <body> <form id="form1" runat="server"> <div> <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true"> <asp:ListItem>list1 item1</asp:ListItem> <asp:ListItem>list1 item2</asp:ListItem> </asp:DropDownList> <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged"> </asp:DropDownList> <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList3_SelectedIndexChanged"> </asp:DropDownList></div> </form> </body> </html> 跟踪网页的执行你会发现第二次选dropdownlist1的时候,dropdownlist1的postback event发生了，但是同时dropdownlist3的postback event也发生了，可是实际上这个postback是list1发生的，和list3无关的，至少在client端时这样的。
.net 2.0, 1.1都测试了，一样地结果。
不知道这算是bug，还是viewstate的问题(by design?)。
