C# .DLL Developer for Excel Add-in

I want a secure .DLL written in C# that will work as an Excel add-in. This Excel add-in should take multiple Excel files from a specified folder, merge them one after another into a single Excel file, and consolidate them into an additional Excel file.

With a “Merge Excel” button, the user will select the Excel files to merge and choose a location. After this, these Excel files should be appended one below the other in the new file.

There are some potential issues we might encounter here. For example, what if the total number of rows in the Excel files we want to merge exceeds Excel’s maximum row limit? (As you know, Excel’s maximum row count is 1,048,576.)

Let’s say we have 10 Excel files to merge, each containing 200,000 rows of data. That’s a total of 2,000,000 rows. At first glance, this might seem like it could fit into two Excel files (1,000,000 rows each), but in practice, it’s not ideal. You can imagine that working with Excel files containing 1 million rows applying filters, creating pivots, etc. is extremely slow and almost unusable.

To handle this, we can add a feature: when saving the file, if the combined data exceeds Excel’s row limit, a button or option could allow splitting the data into separate files after a specified number of rows (e.g., 500,000 rows per file). This would solve the problem by creating four Excel files of 500,000 rows each in this example.

Apart from this, if there are other errors or issues you think might come up, I’d be happy to discuss and hear your suggestions on how to handle them.