string sql = "SELECT * FROM KKK";
            string connectionString;

            // DataTable сохраняет данные в памяти как таблицу
            DataTable dataTable = new DataTable();

connectionString =
            "data source = localhost; Initial Catalog = kkkk;" +
             "Integrated Security = SSPI";
        SqlConnection connection = new SqlConnection(connectionString);

      connection.Open();
        
        SqlCommand sqlCommand = new SqlCommand(sql, connection);
        //Создаем адаптер
        
        dataAdapter = new SqlDataAdapter(sqlCommand);

       
        SqlCommandBuilder commandBuilder =
            new SqlCommandBuilder(dataAdapter);
        
       
        dataAdapter.Fill(dataTable);
        
        dataGridView.DataSource = dataTable;
      
        connection.Close();