I have an MVC3 application running under .NET 4.0 and when I use JavascriptSerializer.Deserialize I'm getting an error.

Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.

Reading Can I set an unlimited length for maxJsonLength in web.config I put the jsonSerialization maxJsonLength key in my web.config but it gets ignored. Though I can set the JavaScriptSerializer.MaxJsonLength property in code and it works fine.

I would like to have the value in the Web.config rather than code. Here is how I am using JavaScriptSerializer.

Dim client As New WebClient

...

Dim result = _client.DownloadString(Test)

Dim serializer = New JavaScriptSerializer

Return serializer.Deserialize(Of Foo)(result)

Here is my Web.config

<configuration>

    <configSections>

    ...

    </configSections>

    <appSettings>

    ...

    </appSettings>

    <system.web>

    <customErrors mode=On>

      <error statusCode=404 redirect=/Http404/>

      <error statusCode=403 redirect=/Http403/>

      <error statusCode=550 redirect=/Http550/>

    </customErrors>

    <compilation debug=true targetFramework=4.0/>

    <pages controlRenderingCompatibilityVersion=4.0>

      <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.web.extensions>

    <scripting>

      <webServices>

        <jsonSerialization maxJsonLength=50000000/>

      </webServices>

    </scripting>

    </system.web.extensions>

 <system.webServer>

 ....

</system.webServer>

</configuration>