First: sorry for the late reply as I had another task to finish.
Second: let me describe my problem in detailed..
I have a dataset consists of more than 50 Feature class, all of them are projected into (Proj1) system.
The features inside every FC are located in 3 regions, My task is to reproject the features based on their regions, i.e. every region has its own transformation parameters to be projected to (Proj2) system.
For every feature class, I need to split it into 3 feature classes based on its region, and then project each one of them separately by custom transformation parameters to (Proj2) system.
So at the end I should have for every feature class in (Proj1) system, 3 resulted feature classes projected into (Proj2) system.
Now I should merge them back again into 1 feature class projected into (Proj2) system.
All that is not a big deal, except this constraint: I have to maintain the OID!! as there are other systems that are linked with these FCs via the OID.
This means simply I want for every Fc to (Split, Project, Merge) the features with maintaining the OID.
This is my problem in detail, hope its clear.
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My first thought of it is to try to edit in the OId after finishing the projection and merging. however I think its not doable at all!
Now am thinking of another way, to do the following:
1-Loop on the features in the FC and project their geometry and store their new location.
2- modify the projection of the FC to be (Proj2) directly.
This should be a long operation (as I have about 3 million feature), however it will do the task with maintaining the OID.
So what do you think ?