Npgsql bulk insert with binary format and typemap

NpgsqlBulkInsertTest.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Npgsql;
using System.Linq.Expressions;
using System.Reflection;
namespace LambdaTest
{
    using CacheFuncType = System.Action<NpgsqlBinaryImporter, object>;
    static class Class1
    {
        static Dictionary<Type, CacheFuncType> FuncCache = new Dictionary<Type, CacheFuncType>();
        static Dictionary<Type, object> CreateValuemap(long idx)
        {
            return new Dictionary<Type, object>()
            {
                { typeof(long),idx }
                ,
                { typeof(string),"mogemoge"+idx.ToString() }
                ,
                { typeof(DateTimeOffset),DateTimeOffset.Now }
            };
        }
        static Expression<CacheFuncType> CreateWriteLambda(Type t)
        {
            var source = Expression.Parameter(typeof(object), "source");
            var objparam = Expression.Parameter(typeof(NpgsqlBinaryImporter), "writer");
            var emethod = Expression.Call(objparam, "Write", new Type[] { t }, Expression.Convert(source, t));
            return Expression.Lambda<CacheFuncType>(emethod, objparam, source);
        }
        static void BulkInsertTest(NpgsqlConnection con)
        {
            var sw = new System.Diagnostics.Stopwatch();
            sw.Start();
            using (var writer = con.BeginBinaryImport("copy test2(a,b,c) from stdin(format binary)"))
            {
                for (int i = 0; i < 1000000; i++)
                {
                    writer.StartRow();
                    //writer.Write((long)i);
                    //writer.Write(string.Format("mogemoge{0}", i));
                    //writer.Write(DateTimeOffset.Now);
                    var valueMap = CreateValuemap(i);
                    foreach (var kv in valueMap)
                    {
                        if (!FuncCache.ContainsKey(kv.Key))
                        {
                            var lambda = CreateWriteLambda(kv.Key);
                            FuncCache[kv.Key] = lambda.Compile();
                        }
                        FuncCache[kv.Key].Invoke(writer, kv.Value);
                    }
                }
            }
            Console.WriteLine($"{sw.Elapsed}");
        }
        public static void Test()
        {
            var cb = new NpgsqlConnectionStringBuilder();
            cb.Host = "localhost";
            cb.Port = 5432;
            cb.Database = "test";
            cb.Username = "testuser";
            cb.Password = "hogehoge";
            cb.CommandTimeout = 0;
            
            using (var con = new NpgsqlConnection(cb))
            {
                con.Open();
                using (var cmd = con.CreateCommand())
                {
                    cmd.CommandText = "truncate table test2";
                    cmd.ExecuteNonQuery();
                }
                BulkInsertTest(con);
            }
        }
    }
}