We need a preview for our application which should show the part file in windows forms Application details: 64 – Bit Framework 4.0 A procedure, we follow: We followed edrawings 64 bit API to generate emodelview.dll and emodelhostcontrol.dll. Then we added these two dll's in our solution to generate an application extension file (.dll) named example.dll. Then we used this application extension file (example.dll) in SolidWorks adding solution to generate an add-on file (swaddin.dll). Then, while using Solidworks using swadddin.dll we accessed example.dll, in this we called edrawings viewer. It works fine. Then after viewing we tried to export a part document as a sat file using both API and manual save as a process. It failed to export, and showing error "The Add-In selected is not a valid SOLIDWORKS Add-In" and not exporting. Once SolidWorks is restarted the sat export works file till our application’s preview is used (our all other application process works file till preview). We are using edrawings 64-bit application extension file. We need a solution to show the preview for part file in windows forms.