<PackageReference Include="System.Reactive" Version="7.0.0-preview.1" />

System.Reactive.Joins.Pattern<TSource1>

public class Pattern<TSource1> : Pattern
namespace System.Reactive.Joins { public class Pattern<[System.Runtime.CompilerServices.Nullable(2)] TSource1> : Pattern { public Plan<TResult> Then<[System.Runtime.CompilerServices.Nullable(2)] TResult>(Func<TSource1, TResult> selector); } }