C++

  bool AddAnnotationText(
        CRhinoDoc& doc,       // reference to active document
        const ON_3dPoint& pt, // location of anotation text
        const wchar_t* text,  // the text
        double height,        // height of text item
        const wchar_t* font,  // font or face name
        int style             // style 0=normal, 1=bold,
        )                     //       2=italic, 3=bold and italic
  {
    bool rc = false;


    ON_wString wText( text );
    if( wText.IsEmpty() )
      return rc;


    if( height <= 0 )
      height = 1.0;


    ON_wString wFont( font );
    if( wFont.IsEmpty() )
      wFont = L"Arial";


    if( style < 0 || style > 3 )
      style = 0;


    ON_Plane plane = RhinoActiveCPlane();
    plane.SetOrigin( pt );


    ON_TextEntity2* text_entity = new ON_TextEntity2;
    CRhinoAnnotationText* text_object = new CRhinoAnnotationText;
    text_object->SetAnnotation( text_entity );
    text_object->SetTextHeight( height );
    text_object->SetString( wText );
    text_object->SetPlane( plane );
    int idx = doc.m_font_table.FindOrCreateFont( wFont, style & 1, style & 2 );
    text_object->SetFontIndex( idx );


    if( doc.AddObject(text_object) )
    {
      rc = true;
      doc.Redraw();
    }
    else
    {
      delete text_object;
      text_object = 0;
    }
    return rc;
  }

VB.NET (Rhino 4)

  Private Function AddAnnotationText(ByVal doc As MRhinoDoc, _
                                      ByVal pt As IOn3dPoint, _
                                      ByVal text As String, _
                                      ByVal height As Double, _
                                      ByVal font As String, _
                                      ByVal style As Integer) As Boolean
    Dim rc As Boolean = False


    If (String.IsNullOrEmpty(text)) Then Return rc
    If (height <= 0) Then height = 1.0
    If (String.IsNullOrEmpty(font)) Then font = "Arial"
    If (style < 0 Or style > 3) Then style = 0


    Dim plane As New OnPlane(RhUtil.RhinoActiveCPlane())
    plane.SetOrigin(pt)


    Dim text_entity As New OnTextEntity2()
    Dim text_object As New MRhinoAnnotationText()
    text_object.SetAnnotation(text_entity)
    text_object.SetTextHeight(height)
    text_object.SetString(text)
    text_object.SetPlane(plane)


    Dim bold As Boolean = False
    If (style = 1 Or style = 3) Then bold = True
    Dim italic As Boolean = False
    If (style = 2 Or style = 3) Then italic = True
    Dim idx As Integer = doc.m_font_table.FindOrCreateFont(font, bold, italic)
    text_object.SetFontIndex(idx)


    If (doc.AddObject(text_object)) Then
      rc = True
      doc.Redraw()
    End If


    Return rc
  End Function

C# (Rhino 4)

  private bool AddAnnotationText(MRhinoDoc doc, IOn3dPoint pt, string text,
                                 double height, string font, int style)
  {
    bool rc = false;
    if (string.IsNullOrEmpty(text))
      return rc;
    if (height <= 0)
      height = 1.0;
    if (string.IsNullOrEmpty(font))
      font = "Arial";
    if (style < 0 || style > 3)
      style = 0;


    OnPlane plane = new OnPlane(RhUtil.RhinoActiveCPlane());
    plane.SetOrigin(pt);


    OnTextEntity2 text_entity = new OnTextEntity2();
    MRhinoAnnotationText text_object = new MRhinoAnnotationText();
    text_object.SetAnnotation(text_entity);
    text_object.SetTextHeight(height);
    text_object.SetString(text);
    text_object.SetPlane(plane);
    int idx = doc.m_font_table.FindOrCreateFont(ref font, (style & 1) > 0, (style & 2) > 0);
    text_object.SetFontIndex(idx);


    if (doc.AddObject(text_object))
    {
      rc = true;
      doc.Redraw();
    }
    return rc;
  }