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C# Console.ReadKey: ConsoleKeyInfo and ConsoleModifiers

This C# example program uses the Console.ReadKey method. It handles keys as they are pressed.

Console.ReadKey

helps create interactive console programs. It does not require the user to press enter before returning. It can read modifiers such as control. It enables more powerful text programs.

In this program,

we use the Console.ReadKey public static method with no arguments. The return value of the Console.ReadKey method is an instance of the ConsoleKeyInfo struct. You can declare a local variable of this type.Public, private

And: After ReadKey returns, the struct is assigned. You can call instance properties on the struct instance to determine the input.

Struct
C# program that uses Console.ReadKey using System; class Program { static void Main() { Console.WriteLine("... Press escape, a, then control X"); // Call ReadKey method and store result in local variable. // ... Then test the result for escape. ConsoleKeyInfo info = Console.ReadKey(); if (info.Key == ConsoleKey.Escape) { Console.WriteLine("You pressed escape!"); } // Call ReadKey again and test for the letter a. info = Console.ReadKey(); if (info.KeyChar == 'a') { Console.WriteLine("You pressed a"); } // Call ReadKey again and test for control-X. // ... This implements a shortcut sequence. info = Console.ReadKey(); if (info.Key == ConsoleKey.X && info.Modifiers == ConsoleModifiers.Control) { Console.WriteLine("You pressed control X"); } Console.Read(); } } Output (Keys were pressed) ... Press escape, a, then control X ?You pressed escape! aYou pressed a ?You pressed control X

When you hover

your mouse over the local variable of type ConsoleKeyInfo, Visual Studio tells you the type is struct. This means it is a value type and that it is basically immutable. But the local variable can be reassigned.

Note: The ReadKey method will return a new ConsoleKeyInfo instance each time it is called.

The ReadKey method

immediately causes the program execution to stop and wait for the input. However, unlike other Console methods, ReadKey will immediately return when a key has been pressed by the user.

Tip: Modifier keys will not cause the immediate return, so control sequences are possible.

Using Key property

on ConsoleKeyInfo. When you call the Key property accessor on the local ConsoleKeyInfo variable, you are reading the values that were already set in the struct.

Here: The escape key is detected. The enter key does not need to be pressed to cause the program code to resume execution.

The Modifiers property

returns a value of type ConsoleModifiers, which is an enumerated constant. You can call the Modifiers property and immediately test it against the ConsoleModifiers constants, such as ConsoleModifiers.Control.Property

Interaction.

We next emphasize one of the uses for the ReadKey method. With this method, you can create fully interactive console programs in the C# language. This allows you to implement simple games, such as maze programs and adventure games.

You could use

a maze program with a pathfinding algorithm to learn more about graph algorithms and other searching routines. In the old days of computing, many adventure games were implemented in console form.Maze

Summary.

We checked out the Console.ReadKey method. It can be used to read keys from the console window and immediately return the value. You can use the ConsoleKeyInfo struct to then access the values read in your C# code.Console.WriteLine
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