Hi,

I drag and drop AJAX ScriptManager control to the source view of default.aspx, here is the code (the third and fourth lines are for ScriptManager):

<%@ Page Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" Title="Untitled Page" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
Status:
    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">
        <asp:ListItem Selected="True" Value="false">Active</asp:ListItem>
        <asp:ListItem Value="true">Complete</asp:ListItem>
    </asp:DropDownList>

But I found ScriptManager tag is underlined with curly red line. When I mouse hover on ScriptManager tag, I see a tip

Element ScriptManager is not a known element. This can occour if there is a compilation error in the website.

But I could compile and run the site successfully. The bugging thing is that all the AJAX control, such as UpdatePanel is not recognized by VS too.

any idea?

Thx

Tao

From what I know, this is what is happening...

 The cause for this error is, in your web.config look for this tag...and change the tagprefix from default asp to anything else...

<controls>
    <add tagPrefix="ajax" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</controls>

and now change the <asp:UpdatePanel> to <ajax:UpdatePanel> . All your errors should be gone.

 please Let us know if this fixes...
 

This does solve the problem. But I don't understand why. Originally, the AJAX control defined in System.Web.Extensions is registered as tagPrefix = asp. So when I use asp:ScriptManager tag, VS should be able to locate the assembly and recognize it, theoritically. Do you know why I have to replace "asp" prefix with something else, such as ajax?

Thx

Tao

Theoretically I too expected the same. We found this fix on some blog(Thanks to him for posting it), I forget the link!. But it solved the dirty red squiggly lines and I made a note of it. May be, experts here can give hind sight of why and the details behind this...

 Happy Coding :)