How do I create a Line without calling Dispose?
@stefanome a écrit :
I think that this will not work because line is returned inside an using block, which means that it has been disposed by the time it is assigned to l1 or l2.
So, why do you create the new Line with a using statement ?
@stefanome a écrit :
Do I need to dispose it or not?
If I dispose it, I can't do anything with it later.
If I don't dispose it, memory leaks or other bad things will happen.
You do not need to dispose it in the CreateLine function. While an entity (or any DBObject) is added to a Transactiion, it will be automatically disposed when the transaction is disposed.
This will work:
public static Line CreateLine(BlockTableRecord space, Point3d p1, Point3d p2)
{
var trans = space.Database.TransactionManager.TopTransaction;
var line = new Line(p1, p2);
space.AppendEntity(line);
trans.AddNewlyCreatedDBObject(line, true);
return line;
}With:
using (var tr = db.TransactionManager.StartTransaction())
{
var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
var l1 = CreateLine(curSpace, p1, p2);
var l2 = CreateLine(curSpace, p3, p4);
double y = 10.0;
if (l1.GetGeCurve().GetDistanceTo(l2.GetGeCurve()) < y)
l2.ColorIndex = 1;
tr.Commit();
}
But simply doing this is simpler and clearer:
using (var tr = db.TransactionManager.StartTransaction())
{
var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
var l1 = new Line(p1, p2);
curSpace.AppendEntity(l1);
tr.AddNewlyCreatedDBObject(l1, true);
var l2 = new Line(p3, p4);
curSpace.AppendEntity(l2);
tr.AddNewlyCreatedDBObject(l2, true);
double y = 10.0;
if (l1.GetGeCurve().GetDistanceTo(l2.GetGeCurve()) < y)
l2.ColorIndex = 1;
tr.Commit();
}
@stefanome a écrit :
@_gile wrote:
@stefanome a écrit :
I think that this will not work because line is returned inside an using block, which means that it has been disposed by the time it is assigned to l1 or l2.
So, why do you create the new Line with a using statement ?
Because I was doing what the documentation says I should do. My code follows this example.
In the linked example nothing is done with the line outside of the (redundent) using statement used to create the new Line.
@stefanome a écrit :
@_gile wrote:
You do not need to dispose it in the CreateLine function. While an entity (or any DBObject) is added to a Transactiion, it will be automatically disposed when the transaction is disposed.
This makes sense, but it is the opposite of what the documentation says on the second point on this page.
If adding it to the space means adding it to the database, then I don't need to dispose because of the third point, but you are mentioning the transaction, and the second point explicitly says the opposite of what you are saying. (I would say that point 3 ensures that Dispose is called, so I can ignore point 2).
This page of the documentation is not very clear.
We should create new DBObjects in a using statement to ensure the object to be disposed in case the object may not be added to the transaction (e.g. an exception occurs).
For example, this is not safe because if the user don't choose "Yes", the newly created Line won't be diposed.
using (var tr = db.TransactionManager.StartTransaction())
{
var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
var line = new Line(new Point3d(5, 5, 0), new Point3d(12, 3, 0));
var pkr = ed.GetKeywords("\nAdd the line to databse [Yes/No]:", "Yes No");
if (pkr.Status == PromptStatus.OK && pkr.StringResult == "Yes")
{
curSpace.AppendEntity(line);
tr.AddNewlyCreatedDBObject(line, true);
}
tr.Commit();
}Creating the Line in a using statement would be a solution to ensure the line to be disposed whatever the user reply.
using (var tr = db.TransactionManager.StartTransaction())
{
var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
using (var line = new Line(new Point3d(5, 5, 0), new Point3d(12, 3, 0)))
{
var pkr = ed.GetKeywords("\nAdd the line to databse [Yes/No]:", "Yes No");
if (pkr.Status == PromptStatus.OK && pkr.StringResult == "Yes")
{
curSpace.AppendEntity(line);
tr.AddNewlyCreatedDBObject(line, true);
}
}
tr.Commit();
}But immediately adding the Line to the Transaction is also a solution which ensure the Line to be disposed with the Transaction whatever le user reply.
using (var tr = db.TransactionManager.StartTransaction())
{
var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
var line = new Line(new Point3d(5, 5, 0), new Point3d(12, 3, 0));
curSpace.AppendEntity(line);
tr.AddNewlyCreatedDBObject(line, true);
var pkr = ed.GetKeywords("\nAdd the line to databse [Yes/No]:", "Yes No");
if (pkr.Status != PromptStatus.OK && pkr.StringResult == "Yes")
{
line.Erase();
}
tr.Commit();
}
@stefanome a écrit :
(Just exchanging opinions here, it's very clear that you are the one teaching and I'm the one learning 🙂)
@_gile wrote:
This will work:
var l1 = CreateLine(curSpace, p1, p2); var l2 = CreateLine(curSpace, p3, p4);
But simply doing this is simpler and clearer:
var l1 = new Line(p1, p2); curSpace.AppendEntity(l1); tr.AddNewlyCreatedDBObject(l1, true); var l2 = new Line(p3, p4); curSpace.AppendEntity(l2); tr.AddNewlyCreatedDBObject(l2, true);
(I have removed some lines from the quoted code for clarity, and the server screwed up the formatting because it didn't like its own html)
I strongly disagree, the second snippet is not simpler and is not clearer!
"Simpler and clearer" was related to what @daniel_cadext said upper.
Creating and returning new DBObject from an external method may not be a good practice because from the top transaction code block we do not see nothing about the state of this newly created object:
- Has it been added to the Database? (most buit-in methods which retun DBObject(s) let the reponsability to add them to the Datadase to the caller)
- Is it opened for write?
- Has it been disposed? As in your case.
The second snippet is less concise but it directly let you know the newly created lines have been added to the Database and so, are opened for write, without having to check the CreateLine called method.
To write more concise code I use to use some Extension methods library as this one.
using Gile.AutoCAD.Extension;
[...]
using (var tr = Active.Database.TransactionManager.StartTransaction())
{
var curSpace = Active.Database.GetCurrentSpace(OpenMode.ForWrite);
var l1 = new Line(p1, p2);
curSpace.Add(l1);
var l2 = new Line(p3, p4);
curSpace.Add(l2);
tr.Commit();
}
[...]
@stefanome a écrit :
I spent a little time on it this morning, trying to understand what makes an extension an extension. I searched for it on the documentation, but I couldn't figure it out.
Extension methods are not specific to the AutoCAD API. They're part of .NET since C#3.0. You can see this topic and this other one.
