topic Re: what is the use of _AcDb.Handle.IsOne in .NET Forum

what is the use of _AcDb.Handle.IsOne

essam-salah — Wed, 26 Jul 2023 15:46:45 GMT

Hi,

as its a self described title i want to know a use case for _AcDb.Handle.IsOne ?

thanks in advance

Re: what is the use of _AcDb.Handle.IsOne

BlackBox_ — Wed, 26 Jul 2023 16:46:08 GMT

https://help.autodesk.com/view/OARX/2023/ENU/?guid=OARX-ManagedRefGuide-Autodesk_AutoCAD_DatabaseServices_Handle_IsOne

There isn't much use for Handle == 1 (or Entity 0).

Re: what is the use of _AcDb.Handle.IsOne

essam-salah — Sun, 30 Jul 2023 14:49:03 GMT

@BlackBox_

i already read the documentation, another question can we know if the object exists or not using Handle ?

Re: what is the use of _AcDb.Handle.IsOne

_gile — Sun, 30 Jul 2023 16:03:12 GMT

@essam-salah a écrit :

can we know if the object exists or not using Handle ?

You can use the undocumented Database.TryGetObjectId method.

Signature:

public bool Autodesk.AutoCAD.DatabaseServices.Database.TryGetObjectId( Autodesk.AutoCAD.DatabaseServices.Handle objHandle, out Autodesk.AutoCAD.DatabaseServices.ObjectId id)

Re: what is the use of _AcDb.Handle.IsOne

essam-salah — Sun, 30 Jul 2023 16:09:16 GMT

@_gile

thanks for the post, so how to check if the Id is exist?

Re: what is the use of _AcDb.Handle.IsOne

_gile — Sun, 30 Jul 2023 16:13:27 GMT

TryGetObjectId returns true, if the supplied Handle is bound to an ObjectId (and set this ObjectId to the out parameter); false, if the supplied Handle is not bound to an ObjectId (and set the out parameter to OnjectId.Null).

Re: what is the use of _AcDb.Handle.IsOne

daniel_cadext — Sun, 30 Jul 2023 21:56:18 GMT

It’s probably something internal, since it’s been around forever,A handle of One seems to always point to the AcDbBlockTable

“since all databases start with the same handseed value of 1 and go up from there”

I also wonder the purpose of mLow and mHigh? Maybe to increase the address range back in the days of 16bit computers

Sorry if I went off topic

Re: what is the use of _AcDb.Handle.IsOne

artc2 — Mon, 31 Jul 2023 17:26:52 GMT

Handles are 64-bit. mLow and mHigh are to allow 64-bit handles on 32-bit computers.

Re: what is the use of _AcDb.Handle.IsOne

daniel_cadext — Mon, 31 Jul 2023 21:40:39 GMT

Ah, that make more sense