This elementary article was originally posted as “C# Basics: Morse Code Converter Using Dictionaries” at Programmer’s Ranch, and was based on Visual Studio 2010. This updated version uses Visual Studio 2017; all screenshots as well as the intro and conclusion have been changed. The source code is now available at the Gigi Labs BitBucket repository.

Today, we’re going to write a little program that converts regular English characters and words into Morse Code, so each character will be represented by a series of dots and/or dashes. This article is mainly targeted at beginners and the goal is to show how dictionaries work.

We’ll start off by creating a console application. After going File -> New Project… in Visual Studio, select the Console App (.NET Framework) project type, and select a name and location for it. In Visual Studio 2017, you’ll find other options for console applications, such as Console App (.NET Core). While this simple tutorial should still work, we’re going to stick to the more traditional and familiar project type to avoid confusion.

In C#, we can use a dictionary to map keys (e.g. 'L') to values (e.g. ".-.."). In other programming languages, dictionaries are sometimes called hash tables or maps or associative arrays. The following is an example of a dictionary mapping the first two letters of the alphabet to their Morse equivalents:

            Dictionary<char, String> morse = new Dictionary<char, string>();
            morse.Add('A', ".-");
            morse.Add('B', "-...");

            Console.WriteLine(morse['A']);
            Console.WriteLine(morse['B']);

            Console.WriteLine("Press any key...");
            Console.ReadKey(false);

First, we are declaring a dictionary. A dictionary is a generic type, so we need to tell in the <> part which data types we are storing. In this case, we have a char key and a string value. We can then add various items, supplying the key and value to the Add() method. Finally, we get values just like we would access an array: using the [] syntax. Just that dictionaries aren’t restricted to using integers as keys; you can use any data type you like. Note: you’ll know from the earlier article, “The ASCII Table (C#)“, that a character can be directly converted to an integer. Dictionaries work just as well if you use other data types, such as strings.

Here is the output:

If you try to access a key that doesn’t exist, such as morse['C'], you’ll get a KeyNotFoundException. You can check whether a key exists using ContainsKey():

            if (morse.ContainsKey('C'))
                Console.WriteLine(morse['C']);

OK. Before we build our Morse converter, you should know that there are several ways of populating a dictionary. One is the Add() method we have seen above. Another is to assign values directly:

            morse['A'] = ".-";
            morse['B'] = "-...";

You can also use collection initialiser syntax to set several values at once:

            Dictionary<char, String> morse = new Dictionary<char, String>()
            {
                {'A' , ".-"},
                {'B' , "-..."}
            };

Since we only need to set the Morse mapping once, I’m going to use this method. Don’t forget the semicolon at the end! Replace your current code with the following:

            Dictionary<char, String> morse = new Dictionary<char, String>()
            {
                {'A' , ".-"},
                {'B' , "-..."},
                {'C' , "-.-."},
                {'D' , "-.."},
                {'E' , "."},
                {'F' , "..-."},
                {'G' , "--."},
                {'H' , "...."},
                {'I' , ".."},
                {'J' , ".---"},
                {'K' , "-.-"},
                {'L' , ".-.."},
                {'M' , "--"},
                {'N' , "-."},
                {'O' , "---"},
                {'P' , ".--."},
                {'Q' , "--.-"},
                {'R' , ".-."},
                {'S' , "..."},
                {'T' , "-"},
                {'U' , "..-"},
                {'V' , "...-"},
                {'W' , ".--"},
                {'X' , "-..-"},
                {'Y' , "-.--"},
                {'Z' , "--.."},
                {'0' , "-----"},
                {'1' , ".----"},
                {'2' , "..---"},
                {'3' , "...--"},
                {'4' , "....-"},
                {'5' , "....."},
                {'6' , "-...."},
                {'7' , "--..."},
                {'8' , "---.."},
                {'9' , "----."},
            };

           

            Console.WriteLine("Press any key...");
            Console.ReadKey(false);

In the empty space between the dictionary and the Console.WriteLine(), we can now accept user input and convert it to Morse:

            Console.WriteLine("Write something:");
            String input = Console.ReadLine();
            input = input.ToUpper();

            for (int i = 0; i < input.Length; i++)
            {
                if (i > 0)
                    Console.Write('/');

                char c = input[i];
                if (morse.ContainsKey(c))
                    Console.Write(morse[c]);
            }

            Console.WriteLine();

Here, the user writes something and it is stored in the input variable. We then convert this to uppercase because the keys in our dictionary are uppercase. Then we loop over each character in the input string, and write its Morse equivalent if it exists. We separate different characters in the Morse output by a forward slash (/). Here’s the output:

Awesome! 🙂 In this article we used Visual Studio to create a program that converts alphanumeric text into the Morse-encoded equivalent, while learning to use dictionaries in the process.