Excel is not an open-source application, you cannot "have" it. It would make no sense, even practical sense. Who wants to use Excel can use it without your application. It is a proprietary commercial close-source application, that's it. Just forget it.
The usual way of Excel integration is using Office Interop, but I would strongly discourage dealing with such stuff.
It's not too hard to create some control with basic spreadsheet functionality, based in one of the available .NET FCL controls. In case of
System.Windows.Forms, it could be, first of all,
System.Windows.Forms.DataGridView:
DataGridView Class (System.Windows.Forms).
If you do some Web search, you will be able to find some open-source components with already developed spreadsheet functionality. The first one I just found is this:
SpreadsheetLight for .NET Framework.
On the opposite, high-end pole, you can see, for example, open-source Calc, part of LibreOffice, which is the product with its own API. However, I would like to warn you: using it would be quite complicated work. Anyway, please see:
LibreOffice — Wikipedia, the free encyclopedia,
Home | LibreOffice,
LibreOffice 5.2 API Documentation.
—SA
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