# Interacting with External Services in .NET Most often you'll be calling REST services. Depending on the language see [[Calling a REST Service From FSharp|Calling a REST Service From F#]] and [[Calling a REST Service From CSharp|Calling a REST Service From C#]]. Those services will most likely use JSON so you can use the [[Fleece Json Library]] to parse it. REST is the most popular way of exposing APIs but [[gRPC in .NET|gRPC]] has its merits as well. In all cases it will make sense to use [[NodaTime]] when dealing with dates and times, as that library offers a superior API when compared to the built-in one. To send e-mails use [[MailKit]]. For RSS feed parsing see [[Parsing an RSS Feed Using FSharp.Data]].