partial class Examples
{
  public static Rhino.Commands.Result AddLinearDimension(Rhino.RhinoDoc doc)
  {
    Rhino.Geometry.LinearDimension dimension;
    Rhino.Commands.Result rc = Rhino.Input.RhinoGet.GetLinearDimension(out dimension);
    if (rc == Rhino.Commands.Result.Success && dimension != null)
    {
      if (doc.Objects.AddLinearDimension(dimension) == Guid.Empty)
        rc = Rhino.Commands.Result.Failure;
      else
        doc.Views.Redraw();
    }
    return rc;
  }
}

import Rhino
import scriptcontext
import System.Guid

def AddLinearDimension():
    rc, dimension = Rhino.Input.RhinoGet.GetLinearDimension()
    if rc==Rhino.Commands.Result.Success:
        if scriptcontext.doc.Objects.AddLinearDimension(dimension)==System.Guid.Empty:
            rc = Rhino.Commands.Result.Failure
        else:
            scriptcontext.doc.Views.Redraw()
    return rc

if __name__=="__main__":
    AddLinearDimension()