ajax for asp.net2.0中'Sys' is undefined的原因及解决方案

当运行一个asp.net 2.0 ajax web页面或为一个已经存在的web应用程序启用Ajax功能时，原来正确的页面，可能会出现提示“ 'Sys' is undefined “。

引起的原因有很多，最可能的一种是： 在页面上启用Ajax功能，但没有在web.config文件中增加相应的配置。

解决方案：

先新建一个普通的vs2005 web 项目， 查看默认的web.config文件，内容大致如下：

Code
<!-- {cps..0}--><? xmlversion="1.0"encoding="utf-8" ?>
< configuration >
< appSettings />
< connectionStrings />
< system.web >
< compilation debug ="true" />
< authentication mode ="Windows" />
</ system.web >
</ configuration >

然后，再新建一个ASP.NET AJAX-enabled Web site，查看默认的web.config文件，内容大致如下：

Code
<!-- {cps..1}--><? xmlversion="1.0" ?>
< configuration >
< configSections >
< sectionGroup name ="system.web.extensions" type ="System.Web.Configuration.SystemWebExtensionsSectionGroup,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" >
< sectionGroup name ="scripting" type ="System.Web.Configuration.ScriptingSectionGroup,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" >
< section name ="scriptResourceHandler" type ="System.Web.Configuration.ScriptingScriptResourceHandlerSection,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" requirePermission ="false" allowDefinition ="MachineToApplication" />
< sectionGroup name ="webServices" type ="System.Web.Configuration.ScriptingWebServicesSectionGroup,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" >
< section name ="jsonSerialization" type ="System.Web.Configuration.ScriptingJsonSerializationSection,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" requirePermission ="false" allowDefinition ="Everywhere" />
< section name ="profileService" type ="System.Web.Configuration.ScriptingProfileServiceSection,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" requirePermission ="false" allowDefinition ="MachineToApplication" />
< section name ="authenticationService" type ="System.Web.Configuration.ScriptingAuthenticationServiceSection,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" requirePermission ="false" allowDefinition ="MachineToApplication" />
</ sectionGroup >
</ sectionGroup >
</ sectionGroup >
</ configSections >

< system.web >
< pages >
< controls >
< add tagPrefix ="asp" namespace ="System.Web.UI" assembly ="System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
</ controls >
</ pages >
< compilation debug ="false" >
< assemblies >
< add assembly ="System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
</ assemblies >
</ compilation >

< httpHandlers >
< remove verb ="*" path ="*.asmx" />
< add verb ="*" path ="*.asmx" validate ="false" type ="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
< add verb ="*" path ="*_AppService.axd" validate ="false" type ="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
< add verb ="GET,HEAD" path ="ScriptResource.axd" type ="System.Web.Handlers.ScriptResourceHandler,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" validate ="false" />
</ httpHandlers >

< httpModules >
< add name ="ScriptModule" type ="System.Web.Handlers.ScriptModule,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
</ httpModules >
</ system.web >

< system.web.extensions >
< scripting >
< webServices >
</ webServices >
</ scripting >
</ system.web.extensions >

< system.webServer >
< validation validateIntegratedModeConfiguration ="false" />
< modules >
< add name ="ScriptModule" preCondition ="integratedMode" type ="System.Web.Handlers.ScriptModule,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
</ modules >
< handlers >
< remove name ="WebServiceHandlerFactory-Integrated" />
< add name ="ScriptHandlerFactory" verb ="*" path ="*.asmx" preCondition ="integratedMode"
type ="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
< add name ="ScriptHandlerFactoryAppServices" verb ="*" path ="*_AppService.axd" preCondition ="integratedMode"
type ="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
< add name ="ScriptResource" preCondition ="integratedMode" verb ="GET,HEAD" path ="ScriptResource.axd" type ="System.Web.Handlers.ScriptResourceHandler,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" />
</ handlers >
</ system.webServer >
</ configuration >

注意：用后一个web.config文件替换前一个web.config文件，或者将后一个文件的新增部分添加到前一个项目中的web.config文件即可。
主要是粗体部分

<?xml version="1.0"?>
<configuration>
<configSections>
<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
<sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication"/>
<sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="Everywhere" />
<section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication" />
<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication" />
</sectionGroup>
</sectionGroup>
</sectionGroup>
</configSections>

<system.web>
<pages>
<controls>
<add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</controls>
</pages>
<compilation debug="false">
<assemblies>
<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</assemblies>
</compilation>

<httpHandlers>
<remove verb="*" path="*.asmx"/>
<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
<add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
<add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" validate="false"/>
</httpHandlers>

<httpModules>
<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</httpModules>
</system.web>

<system.web.extensions>
<scripting>
<webServices>
</webServices>
</scripting>
</system.web.extensions>

<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<modules>
<add name="ScriptModule" preCondition="integratedMode" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</modules>
<handlers>
<remove name="WebServiceHandlerFactory-Integrated" />
<add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode"
type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
<add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode"
type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
<add name="ScriptResource" preCondition="integratedMode" verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
</handlers>
</system.webServer>
</configuration>