mvc 4 assembly reference missing for Json.Encode

Question

I am trying to call a Json.Encode(...) method in MVC 4 and I'm getting an error: The name 'Json' does not exist in the current context.

I've tried adding System.Runtime.Serialization namespace, which has Json class, but this particular instance of Json class doesn't have Encode method.

What assembly am I missing here?

Here is my exact code:

{ url: '@Url.Action("DeleteDefinitionRule")', editData: 
    { companyCode: 'LO', definitionID:@Html.Raw(Json.Encode(Model.DefinitionID)) } }

Answer 1

1. References in solutions explorer > right click > Add reference
2. Under Assemblies > Framework, search for "System.Web.Helpers" Double click
3. System.Web.Helpers version 2.0.0.0 and click ok. Find the
4. System.Web.Helpers you've just added > right click it > properties.
5. Change "Copy Local" from false, to true

And now @Json.Encode should work.

Update