public static IEnumerable Power(int number, int exponent)
    {
        int counter = 0;
        int result = 1;
        while (counter++ < exponent)
        {
            result = result * number;
            yield return result;
        }
    }

And you implement it like this:

         //Display powers of 2 up to the exponent 8:
        foreach (int i in Power(2, 9))
        {
            Console.Write("{0}", i + "\n");
            Thread.Sleep(2000);
        }

You will see that the results in the command line are delayed. If you take that same logic and you translate it to a function that queries a database like this:

    public static IEnumerable GetData()
    {
        DataTable table = new DataTable();
        using (SqlConnection sqlConnection = new SqlConnection("connectionstring"))
        {
            string commandText = "select chattext from Chat";
            using (SqlCommand sqlCommand = new SqlCommand(commandText, sqlConnection))
            {
                sqlCommand.CommandType = CommandType.Text;
                SqlDataAdapter dataAdapter = new SqlDataAdapter(sqlCommand);
                dataAdapter.Fill(table);
            }

        }
        foreach (DataRow row in table.Rows)
        {
            yield return row["chattext"].ToString();
        }
    }

Then the implementation is similar to the first example's:

        foreach (string s in GetData())
        {
            Console.WriteLine(s + "\n");
            Thread.Sleep(2000);
        }

And the result is the same. Read about the yield keyword on MSDN and check out this StackOverflow article, on which the database example is based.