Change text dot's text programmatically

Something that seems to work

Rhino.DocObjects.ObjRef objref = new Rhino.DocObjects.ObjRef(x);
Rhino.DocObjects.TextDotObject dotObject = objref.Object() as Rhino.DocObjects.TextDotObject;
TextDot tdot = dotObject.Geometry as TextDot;
tdot.Text = y+ tdot.Text.Substring(1, 2);
dotObject.CommitChanges();

Based on