New Post: Memory issue for XSSFWorkbook

I'm testing NPOI and I've to admit that it's awsome! very fast and solid!
But I think there are some memory issue.
When I'm opening a large xlsx the memory goes up and it ends with an NPOI.POIXMLException

I'm talking about 30 MB of files with 1 million rows (I know it's a lot of dates) but I've to work with these files..

Here is my code

IWorkbook wb;
using (FileStream file = new FileStream(excelFilePath, FileMode.Open, FileAccess.Read))
{
if (excelFilePath.ToLower().EndsWith(".xlsx"))
    wb = new XSSFWorkbook(file);  // <- NPOI.POIXMLException
else
    wb = new HSSFWorkbook(file);
}