// print out the results

               Console.Write("{0,-25}", contact);

               Console.Write("{0,-20}", city);

               Console.Write("{0,-25}", company);

               Console.WriteLine();

        }

Notice the call to Read on the SqlDataReader, rdr, in the while loop condition in the code above.  The return value of Read is type bool and returns true as long as there are more records to read.  After the last record in the data stream has been read, Read returns false.

注意在上面代码中的while循环对SqlDataReader对象rdr调用的Read方法。Read方法的返回值为bool，并且只要有记录读取就返回真。在数据流中所有的最后一条记录被读取了，Read方法就返回false。

In previous lessons, we extracted the first column from the row by using the SqlDataReader indexer, i.e. rdr[0].  You can extract each column of the row with a numeric indexer like this, but it isn''''t very readable.  The example above uses a string indexer, where the string is the column name from the SQL query (the table column name if you used an asterisk, *.  String indexers are much more readable, making the code easier to maintain.

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