Triggers
are fired on the database when you use the digitize method found within the Topobase
API. This forced me to look for a client side alternative to accomplish the
same without triggering.
The
following class prompts the user to draw a polyline. The result is stored
within the class. An event allows you to fetch the result after the command has
ended.
/// <summary>
/// Class that prompts the user
to draw a polyline.
/// When the command has ended
it fires an event and the polyline gets cleaned up.
/// The class holds the result
of the user input.
/// </summary>
public class DigitizePolyline
{
#region Variables & Properties
private readonly int _startObjectCount;
private int _endObjectCount;
public Polyline Polyline { get; private set; }
/// <summary>
/// Get the active Autocad drawing
document
/// </summary>
public Document Document { get { return Application.DocumentManager.MdiActiveDocument;
} }
#endregion
#region Constructors
public DigitizePolyline()
{
Document.CommandEnded +=
PlineCommandEnded;
Document.CommandCancelled +=
DocOnCommandCancelled;
_startObjectCount = CountObjects();
}
#endregion
#region Events
public event EventHandler DrawEnded;
protected virtual void OnDrawEnded(EventArgs e)
{
if (DrawEnded != null)
{
DrawEnded(this, e);
}
}
private void DocOnCommandCancelled(object sender, CommandEventArgs e)
{
if (e.GlobalCommandName.ToUpper() ==
"PLINE")
{
_endObjectCount =
CountObjects();
if (_endObjectCount !=
_startObjectCount)
{
//TO DO : Replace this with a
method called from the framework!
Polyline =
GetInsertedPolyLine();
}
Remove();
Document.CommandCancelled -=
DocOnCommandCancelled;
Document.CommandEnded -= PlineCommandEnded;
}
}
private void PlineCommandEnded(object sender, CommandEventArgs e)
{
if (e.GlobalCommandName.ToUpper() ==
"PLINE")
{
Polyline =
GetInsertedPolyLine();
Remove();
Document.CommandEnded -=
PlineCommandEnded;
Document.CommandCancelled -=
DocOnCommandCancelled;
OnDrawEnded(e);
}
}
#endregion
#region Public Methods
public void Draw()
{
Document.SendStringToExecute("_PLINE
", false, false, false);
}
#endregion
#region Private Methods
private void Remove()
{
if (Polyline != null)
{
//Failure to lock the document in
certain contexts will cause a lock violation during the modification of the
database.
using (Document.LockDocument())
{
// Start a transaction
using (Transaction tr =
Document.Database.TransactionManager.StartTransaction())
{
//Get the entity from the
database providing the objectId
var ent = tr.GetObject(Polyline.ObjectId,
OpenMode.ForWrite) as Entity;
//Remove the entity from the
database
if (ent != null)
ent.Erase(true);
//Commit the previously
opened transaction
tr.Commit();
}
}
}
}
private Polyline GetInsertedPolyLine()
{
var lastRes =
Document.Editor.SelectLast();
Polyline pl;
ObjectId objectId =
lastRes.Value[0].ObjectId;
//To prevent conflicts with other
requests, you are responsible for locking a document before you modify it.
//Failure to lock the document in
certain contexts will cause a lock violation during the modification of the
database.
using (Document.LockDocument())
{
// Start a transaction
using
(Document.Database.TransactionManager.StartTransaction())
{
//check what sort of entity you
are dealing with
pl = objectId.GetObject(OpenMode.ForRead) as Polyline;
}
}
return pl;
}
public int CountObjects()
{
var count = 0;
using (var tr =
Document.Database.TransactionManager.StartTransaction())
{
using (Document.LockDocument())
{
//Get the BlockTable for the database
var blockTable =
tr.GetObject(Document.Database.BlockTableId, OpenMode.ForRead) as BlockTable;
//Get the modalspace block table
record
var modalspace =
tr.GetObject(blockTable[BlockTableRecord.ModelSpace], OpenMode.ForRead) as BlockTableRecord;
if (modalspace != null)
{
//Loop through the entitys
in modelspace
count +=
modalspace.Cast<ObjectId>().Count();
}
}
}
return count;
}
#endregion
}
The Class In Action
public class MyCommands
{
private DigitizePolyline _digitizePolyline;
[CommandMethod("DigitizePolyline")]
public void DigitizePolyline()
{
try
{
_digitizePolyline = new DigitizePolyline();
_digitizePolyline.Draw();
_digitizePolyline.DrawEnded
+= PlOnDrawEnded;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void PlOnDrawEnded(object sender, EventArgs eventArgs)
{
_digitizePolyline.Document.Editor.WriteMessage("Polyline ObjectId = " +
_digitizePolyline.Polyline.ObjectId);
}
}
