C # Configuration error defines a duplicate "System.web.extensions/scripting/scriptresourcehandler" section

Today, I met this problem,

Computer system: VS2010 Win7 System IIS7

After I run the Web site configured in IIS, I'm saying: Error code 0x800700b7 configuration error defines duplicate "System.web.extensions/scripting/scriptresourcehandler" section

The problem is that Window7 IIS uses the ASP. NET v4.0 application pool by default.

Workaround: Change the. NETFramework version of the application pool for this site to v2.0,

1: Select Application Pool--Right click on right mouse to add application pool

2: Select the. NET Framework version by image (name fill in)

3: On the running web site, right-click Select Admin Application--Select advanced Settings

4: Select in the application pool, pop up the dialog box, select the one you just added. NET version, click OK.

C # Configuration error defines a duplicate "System.web.extensions/scripting/scriptresourcehandler" section