How to read license files

Question

I googled for this and also searched on StackOverflow, but not many helpful links showed up, so here goes:

I have a requirement as follows (and I know this is probably vague, but this is all the information I have right now):

The user will upload a software license file (and the said software can be anything - it is not specific to a particular software product), and the application will have to read the license file and populate a text box with the license key.

Based on this, my questions are as follows:

1. Is there a standard way to read license files for software products?
2. Do software license files have specific file extensions, or is it something specific to the vendors?
3. Is it possible to recognize a file as a license file?
4. Are there any .NET/C# based parsers which can read license files and extract the key?

Answer 1

1. There is no standard way.
2. No.
3. As a developer you can chose whatever you want to use it as the license file.
4. It depends on the way the software developer chose to proof a license, but mostly no.