Asp.net mvc

Question

Hi All,
how to solve this error ?


Server Error in '/' Application.
Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request.
 Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Could not load file or assembly 'System.Web.Helpers, Version=1.0.0.0, Culture=neutral,
 PublicKeyToken=31bf3856ad364e35' or one of its dependencies.
The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Source Error:


Line 25:<assemblies>
Line 26:<add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
Line 27:<add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
Line 28:<add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
Line 29:<add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>


Source File: C:\Users\ravipstel\Desktop\iisbackup\mvcbasicsitesourcecode\MvcBasicSiteSourceCode\MvcBasicSite\MvcBasicSite\web.config    Line: 27

Assembly Load Trace: The following information can be helpful to determine why the assembly 'System.Web.Helpers, Version=1.0.0.0,
 Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded.


=== Pre-bind state information ===
LOG: DisplayName = System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
 (Fully-specified)
LOG: Appbase = file:///C:/Users/ravipstel/Desktop/iisbackup/mvcbasicsitesourcecode/MvcBasicSiteSourceCode/MvcBasicSite/MvcBasicSite/
LOG: Initial PrivatePath = C:\Users\ravipstel\Desktop\iisbackup\mvcbasicsitesourcecode\MvcBasicSiteSourceCode\MvcBasicSite\MvcBasicSite\bin
Calling assembly : (Unknown).
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Users\ravipstel\Desktop\iisbackup\mvcbasicsitesourcecode\MvcBasicSiteSourceCode\MvcBasicSite\MvcBasicSite\web.config
LOG: Using host configuration file: C:\Users\ravipstel\Documents\IISExpress\config\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Post-policy reference: System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/Temporary ASP.NET Files/vs/7d0beb08/b554687/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/Temporary ASP.NET Files/vs/7d0beb08/b554687/System.Web.Helpers/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/Users/ravipstel/Desktop/iisbackup/mvcbasicsitesourcecode/MvcBasicSiteSourceCode/MvcBasicSite/MvcBasicSite/bin/System.Web.Helpers.DLL.
WRN: Comparing the assembly name resulted in the mismatch: Major Version
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34237