Assembly does not found

Question

I am working on Mongodb with MVC application. During execution of application, got an error by server.

Error : Could not load file or assembly 'system.web.mvc (3)' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

What would i do to fix this error? Please help me.

My web.config file:

    <configuration>
      <connectionStrings>
        <add name="ApplicationServices"
             connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true"
             providerName="System.Data.SqlClient" />
        <add name="MongoDB" connectionString="server=127.0.0.1;database=blog" />
      </connectionStrings>

  <appSettings>
    <add key="webpages:Version" value="1.0.0.0" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  </appSettings>

  <system.web>
    <compilation debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
            <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
            <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
            <add assembly="System.Web.WebPages, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
          </assemblies>
        </compilation>

        <authentication mode="Windows" />

        <authorization>
          <deny users="?" />
        </authorization>

        <profile>
          <providers>
            <clear/>
            <add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider" connectionStringName="ApplicationServices" applicationName="/" />
          </providers>
        </profile>

        <roleManager enabled="true" defaultProvider="AspNetWindowsTokenRoleProvider">
          <providers>
            <clear/>
            <add name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider" connectionStringName="ApplicationServices" applicationName="/" />
            <add name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider" applicationName="/" />
          </providers>
        </roleManager>

        <pages>
          <namespaces>
            <add namespace="System.Web.Helpers" />
            <add namespace="System.Web.Mvc" />
            <add namespace="System.Web.Mvc.Ajax" />
            <add namespace="System.Web.Mvc.Html" />
            <add namespace="System.Web.Routing" />
            <add namespace="System.Web.WebPages"/>
          </namespaces>
        </pages>
      </system.web>

      <system.webServer>
        <validation validateIntegratedModeConfiguration="false"/>
        <modules runAllManagedModulesForAllRequests="true"/>
      </system.webServer>

      <runtime>
        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
          <dependentAssembly>
            <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
            <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="3.1.0.0" />
          </dependentAssembly>
        </assemblyBinding>
      </runtime>
    </configuration>