Using a modal .NET dialog to display AutoCAD object properties

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Firstly, a big thanks for all your comments on the first anniversary post. It's good to know that people are finding this blog useful, and I hope the flow of ideas (internal and external) doesn't dry up anytime soon. So keep the comments coming! :-)

This post is going to start a sequence of posts that look at how to integrate forms into AutoCAD. This post looks at modal forms, and later on we'll look more at modeless forms and - in particular - palettes.

Just to be clear, these posts will focus on the basic integration - the more advanced activity of detailed property display (etc.) are left as an exercise for the reader. For example, in today's code we're simply going to get the type of an object and put that text into our dialog. Nothing very complex, but it shows the basic interaction between AutoCAD objects and WinForms.

Before we get started, I should very quickly define "modal" and "modeless", for those that aren't familiar with the terminology. Modal dialogs take exclusive control of an application's user-input functions, while modeless dialogs can co-exist with other modeless dialogs and user-input handling. Which means that the two types of dialog have different issues to deal with (in terms of how the assumptions they make on accessing data etc.).

So next we need to create our form... I'm not going to step through the process here - we'll focus on the code - so to make life easier I've packaged up the source here.

Here's the C# code for the command class. It's very simple: it checks the pickfirst selection and uses the first object as input for the form (assigning the object ID to the form, which will then go away and retrieve the object's type). At this stage we're just supporting one object - we're not going through the effort of determining shared properties across objects etc. We then use Application.ShowModalDialog() to show the form inside AutoCAD.

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;
using System;
using CustomDialogs;

namespace CustomDialogs
{
  public class Commands
  {
    [CommandMethod("vt",CommandFlags.UsePickSet)]
    public void ViewType()
    {
      Editor ed =
        Application.DocumentManager.MdiActiveDocument.Editor;

      TypeViewerForm tvf = new TypeViewerForm();
      PromptSelectionResult psr =
        ed.GetSelection();
      if (psr.Value.Count > 0)
      {
        ObjectId selId = psr.Value[0].ObjectId;
        tvf.SetObjectId(selId);
      }
      if (psr.Value.Count > 1)
      {
        ed.WriteMessage(
          "/nMore than one object was selected: only using the first./n"
        );
      }
      Application.ShowModalDialog(null, tvf, false);
    }
  }
}

The form itself is a little more complex (but barely). It contains a function that can be used to set the active object (by its ID, as mentioned above) which goes away and opens the object, getting its type. The form also contains a "browse" button, which can be used to change the actively selected object.

Here's the C# code for the form:

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace CustomDialogs
{
  public partial class TypeViewerForm : Form
  {
    public TypeViewerForm()
    {
      InitializeComponent();
    }

    public void SetObjectText(string text)
    {
      typeTextBox.Text = text;
    }

    public void SetObjectId(ObjectId id)
    {
      if (id == ObjectId.Null)
      {
        SetObjectText("");
      }
      else
      {
        Document doc =
          Autodesk.AutoCAD.ApplicationServices.
            Application.DocumentManager.MdiActiveDocument;
        Transaction tr =
          doc.TransactionManager.StartTransaction();
        using (tr)
        {
          DBObject obj = tr.GetObject(id, OpenMode.ForRead);
          SetObjectText(obj.GetType().ToString());
          tr.Commit();
        }
      }
    }
    private void closeButton_Click(object sender, EventArgs e)
    {
      this.Close();
    }

    private void browseButton_Click(object sender, EventArgs e)
    {
      DocumentCollection dm =
        Autodesk.AutoCAD.ApplicationServices.
          Application.DocumentManager;
      Editor ed =
        dm.MdiActiveDocument.Editor;

      Hide();
      PromptEntityResult per =
        ed.GetEntity("/nSelect entity: ");
      if (per.Status == PromptStatus.OK)
      {
        SetObjectId(per.ObjectId);
      }
      else
      {
        SetObjectId(ObjectId.Null);
      }
      Show();
    }
  }
}

Here's what happens when you run the VT command and select a circle:

As an aside... I'm going on holiday on Wednesday for a week. We have our annual football (meaning soccer, of course) tournament being held this year in the UK. Teams from Autodesk offices from around the world (it used to have a European focus, but it's gained in popularity in the last few years) will fly in and take part. I'll be playing for one of the Swiss teams, and it'll certainly be lots of fun to catch up with old friends from other locations. The tournament is at the weekend, but I'm taking some days off either side to catch up with family and friends. I doubt I'll have time to queue up additional posts for while I'm away, so this is just to let you know that things may go a little quiet for the next week or so.

June 25, 2007 in AutoCAD, AutoCAD .NET | Permalink