Seems as though this should be in the documentation. If you gentlemen have found it there, would you mind posting the page in the Developer docs? Thanks!
Are you asking why/when the LockDocument() should be used? The OP's issue is due to the fact he uses a modeless form and tries to modify drawing data from the modeless form, thus locking document is needed.
In the Autodesk .NET development guide onlie (http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%20.N
Now that you mention it, I think that is what I am asking. :-) I am having a large degree of difficulty updating (even attaching) an Object Data record from a WinForm in C# with Map 2011. (I created a separate post on the issue.) I will check out the reference and see if it sheds any light on my difficulty. (I have included the lock document code that you mentioned but I'm afraid that the issue is over my head and the "error message" from Autodesk is a little too explicit for my young ears (in other words, it's extremely vague).
Really appreciate you responding so quickly!
Ok, I see that the drawing may have to be locked here. I will attempt to correctly lock the document and see if this solves the problem.
Thanks so much!!
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