WebRequestHandler: .net >=4.5
HttpClientHandler: .net >=4.5 OR netcore >=1.0 OR .NET Standard>=1.1
HttpClientHandler has better performance. So, we should use HttpClientHandler everywhere.
WebRequestHandler open and close a tcp port every request and leaving it in TIME_WAIT state.
HttpClientHandler's keepalive feature reuse existing connections instead.
WebRequestHandler: .net >=4.5 HttpClientHandler: .net >=4.5 OR netcore >=1.0 OR .NET Standard>=1.1 HttpClientHandler has better performance. So, we should use HttpClientHandler everywhere.