how to create error log file in asp net mvc using c# (text file andsql

You can achive this through multple ways, Following are code example and you can select according to your choice:

 

NLog:

NLog is a flexible and free logging platform for various .NET platforms, including .NET standard. NLog makes it easy to write to several targets.

https://www.c-sharpcorner.com/blogs/sample-logging-using-nlog

 

Exception Logging to Text file

https://www.c-sharpcorner.com/UploadFile/0c1bb2/logging-excetion-to-text-file/

 

ASP.NET MVC 5: Logging Exceptions in Database

https://www.dotnetcurry.com/aspnet-mvc/1260/exception-handling-logging-aspnet-mvc