C# - Console.ReadLine Example

Console.ReadLine. This method reads input from the console—when the user presses enter, it returns a string. We can process this string like any other in a C# program.

C# programs will often use the Console.ReadLine method in a loop. With ReadLine() method calls we can repeatedly prompt for input.

Console.WriteLine

Example. When developing programs, we will often want to loop through user inputs. This example uses a while-true loop and the Console.ReadLine() method.

Part 1 With a while-true loop the code loops infinitely. The loop will only exit with a special "exit" command.

while

Part 2 We print a prompt and then read in a line from the console by calling Console.ReadLine.

String Length

Part 3 We check the string returned, and if it equals "exit," the program terminates. We show the length for each string typed.

break

using System; class Program { static void Main() { // Part 1: loop indefinitely. while (true) { // Part 2: get user input with a prompt. Console.WriteLine("Enter input:"); string line = Console.ReadLine(); // Part 3: check string and report output. if (line == "exit") { break; } Console.Write("You typed "); Console.Write(line.Length); Console.WriteLine(" character(s)"); } } }

Enter input: Dot You typed 3 character(s) Enter input: Net Perls You typed 9 character(s) Enter input:

Integer input. Here we use the string from Console.ReadLine as an integer value. We can invoke the int.TryParse method to see if the result string is an integer representation.

Step 1 The line variable is assigned to the reference of the string data allocated by Console.ReadLine and filled with the input.

Step 2 The int.TryParse static method tests for a numeric value, and if this test succeeds we can then use the integer.

int.Parse

Step 3 This program tries to multiply an integer value received by the user by 10 and display the product.

using System; class Program { static void Main() { // Step 1: read string from console. Console.WriteLine("Type an integer:"); string line = Console.ReadLine(); // Step 2: try to parse the string as an integer. int value; if (int.TryParse(line, out value)) { // Step 3: multiply the integer and display it. Console.Write("Multiply integer by 10: "); Console.WriteLine(value * 10); } else { Console.WriteLine("Not an integer!"); } } }

Type an integer: 4356 Multiply integer by 10: 43560

Note, finally. We can insert a Console.ReadLine method call at the end of the Main method—or even in a finally block in the Main method. This will keep the terminal window open.

finally

Summary. With the Console.ReadLine method, part of the System namespace, we can get a string from the console window. We can use the string to control a loop or exit the program.