'Sys undefined'

First, search Baidu and Google for the keyword "sys undefined". You will find that you can search for thousands of records, but to sum up the root cause of the problem is nothing more than the following. However, it seems that I have not found a solution on the Internet.
First
First, let's take a look at the online problems. Although the comrades are all "sys undefined", the situations are different. Some people use the Atlas version, and some use the Asp.net Ajax version.
Beta, and some are officially released Asp.net Ajax beta, so the solution is different. The following briefly summarizes several existing methods:
1. Web. config configuration problems:
Configure the phase joints in Web. config as follows, and then recompile your Program : Program code <Remove verb = "*" Path = "*. asmx"/>
<Add
Verb = "*" Path = "*. asmx" Validate = "false"
Type = "Microsoft. Web. Script. Services. scripthandlerfactory,
Microsoft. Web. Extensions, version = 1.0.61025.0, culture = neutral,
Publickeytoken = 31bf3856ad364e35 "/>
<Add verb = "get" Path = "scriptresource. axd" type = "Microsoft. Web. Handlers. scriptresourcehandler" Validate = "false"/>
</Httphandlers>
<Compilation DEBUG = "true">
<Assemblies>
<Add Assembly = "Microsoft. Web. Extensions, version = 1.0.61025.0, culture = neutral, publickeytoken = 31bf3856ad364e35"/>
</Assemblies>
</Compilation>

If an error persists, write <asp: scriptmanager id = "scriptmanager1" runat = "server" asyncpostbacktimeout = "200"/> In the <form> flag.

2. Permission issues:
This type of error occurs when an anonymous user cannot access the axd file. For more information, see Asp.net Ajax Script Error: SYS undefined solution. the author has a detailed discussion here.

3. Problems with IIS may also cause such errors due to the IIS version. For example, if the operating system of your server is 2000 Server, You need to upgrade them to the latest version, this is mainly for IIS upgrades. Win2003 users can download the relevant patch http://download.microsoft.com/download/7/ B /1/7b1f473c-547d-4196-b00d-bf3aa2a3e898/WindowsServer2003-KB912812-x86-CHS.exe from the address below (we recommend that you install SP2 and update the upgrade in real time)
We can also take a look at the discussion here: blog garden-http://www.cnblogs.com/ltc31/archive/2006/09/20/510003.html

4. Class Library problems:
It would be easier to solve the problem here. You just need to follow the steps below.
To http://ajax.asp.net/downloads/beta/default.aspx? Tabid = 47 & subtabid = 471 download a library file and decompress it to X: \ Program Files \ Microsoft ASP. net \ ASP. NET 2.0 Ajax extensions \ v1.0.61025 (X indicates your installation path drive letter)
You can.

5. Some people mentioned that IP address access may cause problems. localhost or domain name is normal. Here I guess it is a cache problem. You can update the cache to see if it can solve the problem.

6. In addition, if your anti-virus software is sensitive, some JS programs may be killed to generate such problems.

7. Of course, you must first check that your browser does not prohibit JavaScript scripts (this should be confirmed as early as possible)

8,
My own solution: I did not solve the problem well after trying the above methods, so I put all the Asp.net
Delete all the Ajax stuff, including toolkits, and then re-download the latest version of Ajax from Asp.net to install it. The problem is solved simply. After the installation is successful
The vs toolkit has two tabs, Ajax extions and Ajax toolkits, which I do not have after installation ......
You may also try it. It is reasonable to say that it can be used normally after the installation is complete.

9. Program problems: if you have your own Javascript in the programCodeYou need to carefully check the code executed by the client to see if some variables are used before undefined. Pay special attention to the loading order, in short, this is also a cause of the definition of the Sys type.