Transactions

using System.Data.SqlClient;

namespace ConsoleApp1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var cs = @"Server=EGORBO\SQLEXPRESS;Database=testo;User Id=sa;Password=qwerty123;";
            using (var connection1 = new SqlConnection(cs))
            {
                connection1.Open();
                using (var connection2 = new SqlConnection(cs))
                {
                    connection2.Open();
                    Exec(connection2, "BEGIN TRANSACTION;");
                    Exec(connection2, "UPDATE Table_1 SET FOO = 2;");
                    connection2.Close();
                }
                //it won't execute, Table_1 is locked
                Exec(connection1, "UPDATE Table_1 SET FOO=3;");
            }
        }
        
        private static void Exec(SqlConnection c, string s)
        {
            using (var m = c.CreateCommand())
            {
                m.CommandText = s;
                m.ExecuteNonQuery();
            }
        }
    }
}