Ошибка подключения к БД (The login failed)

  string connectionString = @"Data Source=IVAN\SERVER;Initial Catalog=DB_Base;Integrated Security=True;";
string commandText = "Тут запрос";
 
using (SqlConnection connection = new SqlConnection(connectionString))
            {
                SqlCommand cmd = new SqlCommand(commandText, connection);
                connection.Open();
                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    reader.Read();
                    try
                    {
                        Access = reader["Access"].ToString();
                    }
                    catch
                    {
                        Access = "denied";
                        return Access;
                    }
                    
                }
            }

string connectionString = @"Data Source=IVAN\SERVER;Initial Catalog=DB_Base;"+"Integrated Security=SSPI;Pooling=False";

 @"Provider=SQLOLEDB;Data Source=IVAN\SERVER;Initial Catalog=DB_Base;Integrated Security=SSPI;"

 string connectionString = @"Provider=SQLOLEDB;Data Source=IVAN\SERVER;Initial Catalog=DB_Base;Integrated Security=SSPI;";

OleDbConnection conn = new OleDbConnection(@"Provider=SQLOLEDB;Data Source=IVAN\SERVER;Initial Catalog=DB_Base;Integrated Security=SSPI;");
            conn.Open();