>>>I'm seeing a number of Open Source libraries on CodePlex (e.g. NPOI, EPPlus, ClosedXML, etc.)
>>>
>>>My requirements are that I need to read and write Excel spreadsheets and they might be in the old XLS format as well as the newer XLSX format.
>>>
>>>I see that NPOI says it supports XLS, XLSX, and DOCX where as the others don't support XLS.
>>>
>>>Suggestions?
>>
>>I've used NPOI and it has worked. I can't compare it to the others, but if I needed to do Excel work in the future I would start with that library.
>
>Mike,
>
>I'm looking at NPOI and trying to get the examples to run, but I can't make heads or tails out of it and it says that I'm missing references even thought I did a "Install-Package NPOI"

Sorry, it's been a few years since I've used it. I wonder if the NuGet package is fubar'ed? Or maybe you're using functionality that isn't in one of the base references?