Hi, I have an application that write huge .csv files about the size ranging from 1 GB to 2 GB. I need to color code the file and save it as .xlsx. So I have tried using Excel Interop and it works great for small files, but when I try to open a 1.3 GB .csv file with Excel, I get an Hresult error. Any ideas as to how I could accomplish this task either with using Excel, or if there is any other way of doing it. Thanks!