1) Compile your app to 64 bits (to get rid of Out of Memory exception)
2) Turn off events (to speed up the process)
var wb = new XLWorkbook(XLEventTracking.Disabled);
https://closedxml.codeplex.com/wikipage?title=Turning%20off%20events&referringTitle=Documentation
2) Turn off events (to speed up the process)
var wb = new XLWorkbook(XLEventTracking.Disabled);
https://closedxml.codeplex.com/wikipage?title=Turning%20off%20events&referringTitle=Documentation