BUG #14433: Bulk insert

The following bug has been logged on the website:

Bug reference: 14433
Logged by: zeinab mokdad
Email address: zmokdad(at)vanrise(dot)com
PostgreSQL version: 9.6.1
Operating system: Windows
Description:

using Npgsql 3.1,
I am unable to do a bulk insert of a text file in postgres server.
I am using below to insert object by object.
using (NpgsqlConnection conn = new
NpgsqlConnection(GetConnectionString()))
{
if (conn.State == ConnectionState.Closed) conn.Open();
using (var inStream =
conn.BeginTextImport(string.Format("COPY {0} FROM STDIN", tableName)))
{ inStream.Write(route);
}
}

is there anyway where I can insert the list of object at one hit?