The name `addtaghelper` does not exist in the current context

Question

I'm trying to use ASP.NET 5 Tag Helpers. Having configured server-side error messages, I'm receiving the following:

error CS0103: The name 'addtaghelper' does not exist in the current context

From reading online tutorials, addtaghelper is supposed to exist. In project.json we've added this:

"Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-beta4"

Also, in _ViewStart.cs we have the following:

@addtaghelper "Microsoft.AspNet.Mvc.TagHelpers"

Why does addtaghelper not exist in the current context? How can we add it to the current context?

I've tried camel casing as @addTagHelper but this leads to a new error:

Invalid tag helper directive look up text 'Microsoft.AspNet.Mvc.TagHelpers'. The correct look up text format is: "typeName, assemblyName".

Solution

The answer is in the source on GitHub. This is the directive to add.

@addTagHelper "*, Microsoft.AspNet.Mvc.TagHelpers"

Gotchas:

Quotes are optional (see conversation on GitHub).
The directive is case sensitive and requires camel casing.
To include all tag helpers, we use * for the typeName.
As of today, project.json must have "Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-beta4" in the dependencies section.