OrleansListDynamic.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <LangVersion>7.3</LangVersion>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Orleans.CodeGenerator.MSBuild" Version="2.1.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.Orleans.OrleansRuntime" Version="2.1.0" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using Orleans;
using Orleans.Hosting;

namespace OrleansListDynamic
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var silo = new SiloHostBuilder()
                .UseLocalhostClustering()
                .EnableDirectClient()
                .Build();

            await silo.StartAsync();

            var client = silo.Services.GetRequiredService<IClusterClient>();
            var grain = client.GetGrain<IMyGrain>(0);
            var result = await grain.Echo(
                new List<KeyValuePair<string, dynamic>>
                {
                    new KeyValuePair<string, dynamic>("we", 1),
                    new KeyValuePair<string, dynamic>("have", Guid.NewGuid()),
                    new KeyValuePair<string, dynamic>("liftoff", DateTime.UtcNow),
                });
            Console.WriteLine($"Results ({result.Count}):");
            foreach (var (key, value) in result)
            {
                Console.WriteLine($" * {key} = {value}");
            }
        }
    }

    public interface IMyGrain : IGrainWithIntegerKey
    {
        Task<T> Echo<T>(T value);
    }

    public class MyGrain : Grain, IMyGrain
    {
        public Task<T> Echo<T>(T value) => Task.FromResult(value);
    }
}