If you are getting the error with WinSCP .NET assembly and the error details are like “Request event - System Error. Code: 5. - Access is denied”, the error indicates that the .NET assembly cannot communicate with WinSCP executable. This usually happens, when the .NET assembly is used within a restricted environment like IIS Web Service and the assembly and the process are using different local accounts.
Though in general, WinSCP .NET assembly is not the right tool to be used for web development.