<PackageReference Include="System.Reactive" Version="4.1.2" />

QueryablePattern<TSource1, TSource2, TSource3>

public class QueryablePattern<TSource1, TSource2, TSource3> : QueryablePattern
Represents a join pattern over three observable sequences.
public QueryablePattern<TSource1, TSource2, TSource3, TSource4> And<TSource4>(IObservable<TSource4> other)

Creates a pattern that matches when all four observable sequences have an available element.

public QueryablePlan<TResult> Then<TResult>(Expression<Func<TSource1, TSource2, TSource3, TResult>> selector)

Matches when all observable sequences have an available element and projects the elements by invoking the selector function.