In Ajax: SYS is not defined

1: Add Ajax reference

 

2. Add system. Web. Extensions reference

 

3. Add the selected part in Web. config.

 

4. Add

 

If a script error is reported, sys is not defined ..

You need to add it to Web. config.

<Httphandlers>
<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 = "*" 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>

After compilation, it will be OK.