Sendinblue API can be used by platforms developed in various languages like PHP, Java, Node.js, Python, C# and Ruby.
Integrating send in blue to your site C#
Before Starting If you want to know how to set up the send in blue dashboard before integration click link to know more: How to Integrate Sendinblue Transactional Email
First Download the library from Send in blue GitHub
To add the library to your Project file is after download creates a new folder in your project and add mailinblue.dll which is present in this folder -> \V2.0\mailinblue\bin\mailinblue.dll .
To send attachment/s generated on the fly.
Please note that your email content and attached files size should not be greater than 10 MB.