<PackageReference Include="NETStandard.Library" Version="2.0.3" />

System.Func<T1, T2, T3, TResult>

public sealed delegate Func<T1, T2, T3, TResult> : MulticastDelegate
namespace System { public delegate TResult Func<in T1, in T2, in T3, out TResult> (T1 arg1, T2 arg2, T3 arg3); }