test

using System;
using System.Data.SqlClient;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            var sqlCommandLength = 1024*16; // 702 works as expected, 703 does not.
            var connectionString = "Server=10.0.75.1;Database=testo;User Id=sa;Password=qwerty123;";

            var sql = new string(';', sqlCommandLength);

            foo(connectionString, sql);
            Console.WriteLine("End2");
        }

        static void foo(string connectionString, string sql)
        {
            using (var dbcon = new SqlConnection(connectionString))
            {
                dbcon.Open();
                using (var dbcmd = dbcon.CreateCommand())
                {
                    dbcmd.CommandText = sql;
                    using (var reader = dbcmd.ExecuteReader())
                    {
                        while (reader.Read()) { }
                    }
                }
            }
        }
    }
}