Through the Interface

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.DatabaseServices;

using Autodesk.AutoCAD.Runtime;

 

namespace MTextEditing

{

  public class Commands

  {

    [CommandMethod("CTU")]

    public void ChangeToUppercase()

    {

      ChangeCase(true);

    }

 

    [CommandMethod("CTL")]

    public void ChangeToLowercase()

    {

      ChangeCase(false);

    }

 

    private void ChangeCase(bool upper)

    {

      Document doc =

        Application.DocumentManager.MdiActiveDocument;

      Database db = doc.Database;

      Editor ed = doc.Editor;

 

      // Specifically select an MText object

 

      PromptEntityOptions peo =

        new PromptEntityOptions(

          string.Format(

            "\nSelect MText to change to {0}case: ",

            upper ? "upper" : "lower"

          )

        );

      peo.SetRejectMessage("\nObject must be MText.");

      peo.AddAllowedClass(typeof(MText), false);

 

      PromptEntityResult per = ed.Get
Entity(peo);

      if (per.Status != PromptStatus.OK)

        return;

 

      Transaction tr =

        doc.TransactionManager.StartTransaction();

      using (tr)

      {

        // We only need our MText open for read

 

        DBObject obj =

          tr.GetObject(per.ObjectId, OpenMode.ForRead, false);

        MText mt = obj as MText;

 

        if (mt == null)

          return;

 

        // Create a text editor object for the MText

 

        TextEditor te = TextEditor.CreateTextEditor(mt);

        if (te == null)

          return;

 

        // Select the entire contents of the MText

 

        te.SelectAll();

        TextEditorSelection sel = te.Selection;

        if (sel == null)

          return;

 

        // Check whether we can change the selection's

        // case, and then do so

 

        if (sel.CanChangeCase)

        {

          if (upper)

            sel.ChangeToUppercase();

          else

            sel.ChangeToLowercase();

        }

 

        // Be sure to save the results from the editor

 

        te.Close(TextEditor.ExitStatus.ExitSave);

        tr.Commit();

      }

    }

  }

}