21
Thu, Nov
1 New Articles

TechTip: C# for RPGers - More on Arrays and a Different FOR Loop

General
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

Let’s continue to explore C# arrays and introduce a different FOR loop. It’s a very useful tool that has no equivalent in RPG.

In the last TechTip in this C# series, I introduced the array data type and showed how it’s defined and used. Now let’s explore some of its properties and methods, with the help of a different FOR loop: ForEach.

Let’s use the code from the previous TechTip as a starting point for this one. I’m not going to change that code, but it might be useful to have it at hand to compare code features and for you to play around with what you’ll learn this time. Open the “IntroducingArrays” project, by navigating to the respective folder and opening the “IntroducingArrays.sln” file. Now position the cursor at the end of the myFirstArray definition line (it should be line 9 of the source code) and press Enter. Type, or copy and paste, the following lines of code:

// it's also possible to initialize the array when it's being defined

String[] serverNames = new String[]

                       { "AS/400"

                       , "iSeries"

                       , "System i"

                       , "IBM i" };

This is a different way to define an array, which combines definition and initialization on the same statement. Note that the length of the array is automatically determined by the compiler, based on the number of elements on the list. This piece of code will create a four-element array of strings and initialize it with “AS/400”, “iSeries”, “System i”, and “IBM i”.

Introducing the foreach Loop

Now place the cursor at the end of the last Console.ReadKey(); line and press Enter. To output the values of the serverNames array, I could write a FOR loop, similar to the ones used in the previous TechTip. Actually, I could simply copy and paste the last FOR loop and switch the array name, replacing myFirstArray by serverNames. Instead of doing that, I’ll introduce a different type of FOR loop, created to facilitate the handling of collections of data, like arrays and lists. (By the way, the List data type will be discussed in the next TechTip.) This FOR loop variant, aptly named foreach, allows you to perform a set of operations to each element of a data collection. In this case, I’ll use it to output the value of each element of the serverNames array:

Console.WriteLine("The chronologically sorted string array:");

// looping through the array

// using foreach and outputing each element

foreach (string name in serverNames)

{

Console.WriteLine(name);

}

Console.ReadKey();

Note how simple and elegant this loop structure is. I simply “tell” the compiler the name of the array as well as the data type and name of each of the elements of that array. In this example, I’m using a string variable (after all, my array is an array of strings) called name. The syntax is almost natural English: “for each name in server names do this…”. Then I can use the name variable to refer to each of the elements of the arrayall of this without indexes or iterators.

You’ll see that the foreach loop is particularly useful to iterate over complex data types, either native or user-defined.

More Array Properties and Methods

My serverNames array now contains the names the IBM i has had over the years (assuming I got them all; feel free to correct me) in chronological order. Suppose I want to reorder the elements of the array and switch from a chronological to an alphabetic order. I could write a piece of code to sort the array or look up one of the gazillion versions of that sorting algorithm online. Instead, I’ll use a method of the Array class: the Sort method. If you remember what I explained a few TechTips ago, Visual Studio presents a list of available properties and methods of an object when you type the object name followed by a dot (“.”). However, if you type “serverNames.” you won’t find the Sort method. This and many other methods are not available on the variables defined by the programmer. Instead, they are part of the Array class itself. You’ve seen something similar to this before: I’ve been using the WriteLine method of the Console class to output “things.” However, I didn’t define an object or variable named Console. It’s simply made available by C# (it’s a bit more complicated than this, but this will be enough for now). Similarly, I can invoke methods of the Array class by typing “Array.” and selecting the appropriate method from the list. So now let’s sort the serverNames array by either typing, or copying and pasting, the following code to the line below the last line you inserted (that would be the ReadKey() line):

Array.Sort(serverNames);

To see the result, copy and paste the foreach loop to after the array sorting line. If you run the program, you’ll see first the original, chronologically ordered list of server names and then the same list, now alphabetically sorted. The same conceptually simple type of solution is available for other common problems, such as clearing an array. Naturally, you can use a FOR or foreach loop structure to fly through the entire array, zapping each element’s value. Or you can use Array.Clear.

The Clear method has enough flexibility to scrub clean an entire array or simply a part of it, because it allows you to specify where to start, with the <start position> parameter, and how many elements to clear, with the number of elements from that position on, with the <length to clear> parameter. The method’s complete syntax, which reminds me of the Substring method I discussed in a previous TechTip, is the following:

Array.Clear(<array name>, <start position>, <length to clear>);

If I wanted to clear the serverNames array, I’d simply write:

// clearing an entire array with a single instruction

Array.Clear(serverNames, 0, serverNames.Length);

In order to confirm it’s really scrubbed clean, let’s output the value of the first element of the array:

// showing the first element of the array:

// it's now blank, the default value for a string ("")

Console.WriteLine("And now first position of the array, after being cleared:");

Console.WriteLine(serverNames[0]);

Console.ReadKey();

Feel free to explore the Array class methods and experiment with this piece of code on your own; you’ll find the complete source code of the last two TechTips below. As usual, Visual Studio’s embedded (and online) documentation will guide you through the details, and if that’s not enough, there are tons of forums where you can get help.

Arrays are powerful data structures but suffer from a major design flaw: They can’t be re-dimensioned. Once created, their length will remain the same. You can copy an array’s elements to a new, larger array (using the object’s CopyTo method, which I haven’t explained yet), but you’ll end up with the same problem, eventually. There’s another data structure, with some similarities with the Array but free of this annoying flaw: the List. I’ll be talking about it in the next TechTips.

That’s all the time I have! I’ll leave you with the complete source code of these two TechTips:

using System;

namespace IntroducingArrays

{

   class Program

   {

       static void Main(string[] args)

       {

           int[] myFirstIntArray = new int[10];

           // it's also possible to initialize the array when it's being defined

           String[] serverNames = new String[]

                                   { "AS/400"

                                   , "iSeries"

                                   , "System i"

                                   , "IBM i" };

           // assigining 1 to the first position of the array

           myFirstIntArray[0] = 1;

           // looping through the array, starting on position 1

           for (int index = 1; index <= 9; index++)

           {

               myFirstIntArray[index] = index + 1;

           }

           // displaying the value of the array's third position

           Console.WriteLine(myFirstIntArray[2]);

           // ReadKey is used to "pause" the display

           // until a key is pressed

          Console.ReadKey();

           // looping through the array, to output the value of each element

           for (int index = 0; index < myFirstIntArray.Length; index++)

           {

               Console.WriteLine(myFirstIntArray[index]);

            }

           // ReadKey is used to "pause" the display

           // until a key is pressed

           Console.ReadKey();

           Console.WriteLine("The chronologically sorted string array:");

           // looping through the array

           // using foreach and outputing each element

           foreach (string name in serverNames)

           {

               Console.WriteLine(name);

           }

           Console.ReadKey();

           // sort the array using Array.Sort(<array name>)

           Array.Sort(serverNames);

           // show the array contents again

           Console.WriteLine("Now the alphabetically sorted string array:");

           // looping through the array

           // using foreach and outputing each element

           foreach (string name in serverNames)

           {

               Console.WriteLine(name);

           }

           Console.ReadKey();

           // clearing an entire array with a single instruction

           Array.Clear(serverNames, 0, serverNames.Length);

           // showing the first element of the array:

           // it's now blank, the default value for a string ("")

           Console.WriteLine("And now first position of the array, after being cleared:");

          Console.WriteLine(serverNames[0]);

           Console.ReadKey();

       }

   }

}

Rafael Victoria-Pereira

Rafael Victória-Pereira has more than 20 years of IBM i experience as a programmer, analyst, and manager. Over that period, he has been an active voice in the IBM i community, encouraging and helping programmers transition to ILE and free-format RPG. Rafael has written more than 100 technical articles about topics ranging from interfaces (the topic for his first book, Flexible Input, Dazzling Output with IBM i) to modern RPG and SQL in his popular RPG Academy and SQL 101 series on mcpressonline.com and in his books Evolve Your RPG Coding and SQL for IBM i: A Database Modernization Guide. Rafael writes in an easy-to-read, practical style that is highly popular with his audience of IBM technology professionals.

Rafael is the Deputy IT Director - Infrastructures and Services at the Luis Simões Group in Portugal. His areas of expertise include programming in the IBM i native languages (RPG, CL, and DB2 SQL) and in "modern" programming languages, such as Java, C#, and Python, as well as project management and consultancy.


MC Press books written by Rafael Victória-Pereira available now on the MC Press Bookstore.

Evolve Your RPG Coding: Move from OPM to ILE...and Beyond Evolve Your RPG Coding: Move from OPM to ILE...and Beyond
Transition to modern RPG programming with this step-by-step guide through ILE and free-format RPG, SQL, and modernization techniques.
List Price $79.95

Now On Sale

Flexible Input, Dazzling Output with IBM i Flexible Input, Dazzling Output with IBM i
Uncover easier, more flexible ways to get data into your system, plus some methods for exporting and presenting the vital business data it contains.
List Price $79.95

Now On Sale

SQL for IBM i: A Database Modernization Guide SQL for IBM i: A Database Modernization Guide
Learn how to use SQL’s capabilities to modernize and enhance your IBM i database.
List Price $79.95

Now On Sale

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: