with photoshop ConnectionSDK, How to retrieve app.activeDocument as PSD file?

Dear all,

I'm currently making an automation s/w communicating with PhotoShop via connection sdk.

Even though my primary language is C#, translating Java/iOS sample to C# works fine.

Sending/receiving image file, invoking Javascript snippet work fine as demonstrated in sdk sample.

Also, sending PSD to PhotoShop also works, so that I can send PSD file in my s/w onto PhotoShop.

My question is here, How to retrieve PSD file working in PSD via connection sdk?

Actual goal of my s/w is

1. send predefined PSD onto PhotoShop

2. PhotoShop user does editing with this given psd

3. when editing is done, retrieve PSD from PhotoShop onto my s/w to process further in Asset Management system.

Any advice would be helpful for me, Thanks in advance.