BioMetrix
A ZKteco Device Implementation
Please go through the following link for the full description :
https://www.codeproject.com/Articles/1104538/Csharp-ZKTeco-Biometric-Device-Getting-Started
If you are working with a different version of device like zk4500, slk20m, slk20r or the zk9500, there is a separate article for that as well: https://www.debuggershub.com/c-zkteco-fingerprint-scanner-implementation-zk4500-slk20m-slk20r-zk9500/
Sample Source Code can be found here : https://github.com/zaagan/ZKTecoFingerPrintScanner-Implementation