Visual Studio namespace errors "doc.Objects.FindByLayer", c#

I'm having trouble using the code segment "doc.Objects.FindByLayer" in Visual Studio. The code worked perfectly in the native c# component environment.  

Help is certainly welcome.

// Working code in native c# component

Rhino.DocObjects.Layer lyr = doc.Layers[index];

Rhino.DocOjbects.RhinoObject[] objs = doc.Objects.FindByLayer(lyr);

// Code that was attempted in Visual Studio, c# (namespace errors)

Rhino.DocObjects.Layer lyr = Rhino.DocObjects.ActiveDoc.Layers[index];

Rhino.DocOjbects.RhinoObject[] objs = Rhino.DocObject.Tables.ObjectTable.FindByLayer(lyr);