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EdB · #1 (**permalink**) 05-14-2008

I am using Mappoint with VB.Net. Iam having an issue with delete on a dataset item

I am populating the Datasets with the following code:

Dim objLoc As MapPoint.Location = mpMap.ActiveMap.GetLocation(CDbl(objLocationMaster .Latitude), CDbl(objLocationMaster.Longitude))

mpMap.ActiveMap.AddPushpin(objLoc, strPushPinName)

I then call the following code:

If mpMap.ActiveMap.DataSets.Count > 0 Then
mpMap.ActiveMap.DataSets.Item(1).Delete()
End If

And at what appears to be at random times and intervals, and varying items in the data set, MapPoint will display the following:

---------------------------
Microsoft MapPoint
---------------------------
An invalid argument was encountered.
---------------------------
OK
---------------------------

Any ideas as to what would cause this to occur?

Thanks in advance for any help.

**Wilfried** · #2 (**permalink**) 05-15-2008

Hi,

And which line of code is the offending one?

EdB · #3 (**permalink**) 05-15-2008

Sorry about that. The offending line of code is:

mpMap.ActiveMap.DataSets.Item(1).Delete()

Thanks.

**Wilfried** · #4 (**permalink**) 05-15-2008

Hi,

Strange, since you check the Count property first there must be an Item(1). Maybe a bug that occurs in certain occasions. Best is to put the Delete() into an exception block, in that case you can also comment out the check on the Count;

**Winwaed** · #5 (**permalink**) 05-15-2008

Does VB.Net use 1-referencing or 0-referencing? It is a while since I used it.

I know VB6 uses 1-referencing, but most other languages use 0-referencing.
0-referencing would cause this bug.

As well as adding an exception, you could extract the reference and check it for null before calling Delete.

Richard

EdB · #6 (**permalink**) 05-15-2008

Thanks for the pointers.

VB.Net is indeed 0 based. This syntax is confusing because the "1" is not a direct index it is a Key. DataSets is a collection of DataSet. I am not sure I am explaining that well, does that make sense?

I believe if there was a null reference then when I check the count, it should throw a null reference exception, which is not the case.

The other suggestion about catching the exception would work, however it is not an exception that is being thrown. An actual message box is coming up, in my UI. If I cannot figure out the root cause, it would be fine if there is a way to tell mappoint to suppress messages boxes.

Could it be possible that this is a memory issue? The reason I ask, is this occurs at random times, but always near the end of large task. I am doubtful since I am in managed code, but you never know.

And Thanks again for any help you can give.

**Winwaed** · #7 (**permalink**) 05-15-2008

The documentation says that Datasets is a collection and the Item method expects an index. I believe I've seen this before with MapPoint 'collections' - it means repeated iterations are often required to find an object in a MapPoint collection.

The bit about null: I was thinking that Item() might succeed but return a null. If this is the case, then Delete will fail

Richard

**Wilfried** · #8 (**permalink**) 05-16-2008

Hi,

Quote:

The other suggestion about catching the exception would work, however it is not an exception that is being thrown. An actual message box is coming up, in my UI. If I cannot figure out the root cause, it would be fine if there is a way to tell mappoint to suppress messages boxes.

There is no way to tell mappoint to suppress it. I've never seen this message however.

Quote:

Could it be possible that this is a memory issue? The reason I ask, is this occurs at random times, but always near the end of large task. I am doubtful since I am in managed code, but you never know.

Maybe, I don't know. But you can check out with task manager if it happens when your application or mappoint has eaten a lot of memory.

EdB · #9 (**permalink**) 05-16-2008

Thanks for all the good feedback. I will try to iterate through the collection and see what I see and I will also monitor the memory use.

I will post back with the results no matter the case.

Thanks again.

EdB · #10 (**permalink**) 05-16-2008

OK, I now believe that there is a race condition going on here. Not sure what it is, but whenever I stepped into the debugger the error would not occur. I add a sleep right before the delete and I did not get the error. If the sleep keeps the error from happening then that will be fine. I still would like to know what the actual cause was. Oh well.

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