.NET virus scanning API
I would probably just make a system call to run an independent process to do the scan. There are a number of command-line AV engines out there from various vendors.
Scan uploaded files C# ASP.net
ClamAV has pretty bad detection scores.
VirusTotal is not on premises.
I decided to create CLI wrappers for multiple scanners, nuget packages can be found here: https://www.nuget.org/packages?q=avscan
And its documentation and source code available at https://github.com/yolofy/AvScan
Run a Virus Scan While Uploading files in ASP.NET
Just purchase antivirus software that has a command-line interface (several popular packages include this). Once the file has been uploaded, run the scan.
I would think, in order to upload and scan at the same time, you might need to implement your own antivirus software as I'm not familiar with any package that would provide that sort of interface.
I run a shareware site. It doesn't work as you described, but I download each file to my local computer and run a scan on them. You would be doing something similar.
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