Console I/O: Reading & Writing

In Plain English

Interactive applications communicate with users. Console.WriteLine() prints a line and advances the cursor, Console.Write() prints without a newline, and Console.ReadLine() captures user keyboard text. To convert text into numbers, use Convert.ToInt32() or int.Parse().

The Mental Model

"Console.WriteLine() is like sending a text message and hitting send. Console.Write() is typing letters without hitting send. Console.ReadLine() is waiting for the user to type a reply and press Enter."

Deep Dive: How It Works

Console.WriteLine(text): Prints text with an automatic trailing newline.

Console.Write(text): Prints text without advancing to the next line (perfect for input prompts: Console.Write("Enter name: ");).

Console.ReadLine(): Reads a full line of text entered by the user as a string.

Type Parsing: Console.ReadLine() always returns a string. To convert to an int: int age = int.Parse(Console.ReadLine()); or int age = Convert.ToInt32(Console.ReadLine());.

Syntax Blueprint

Console.Write("Enter name: ");
string name = Console.ReadLine();
Console.WriteLine("Hello, " + name);

Prompt with Write(), capture with ReadLine(), echo with WriteLine().

Core Rules to Remember

Write vs WriteLine: Write() keeps cursor on same line; WriteLine() adds a newline.

ReadLine Returns String: Always returns string data that must be parsed if numeric.

Safe Parsing: int.TryParse() is used in production to safely handle invalid numeric user input.

Common Beginner Traps & How to Fix Them

Mistake:Trying to assign ReadLine directly to an int: int age = Console.ReadLine();

Why it happens: Expecting automatic type casting.

How to fix: Wrap in int.Parse(): int age = int.Parse(Console.ReadLine());.

Pro Tip: Use int.TryParse(input, out int result) to convert user input without crashing if they type letters instead of numbers!

Live Interactive Example

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Console Formatting & Parsing

C# 12 / .NET

Output Console

Click "Run Code" to view the rendered output.

How it works: The string "25" is parsed into an int and used in an arithmetic calculation.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Parse string to integer

Declare string inputScore = "85";
Parse it into int score = int.Parse(inputScore);
Print "Final Score: 85".

Sandbox Output

Click "Run & Check" to test your solution.

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Deep Dive: How It Works

Console.WriteLine(text): Prints text with an automatic trailing newline.

Console.Write(text): Prints text without advancing to the next line (perfect for input prompts: Console.Write("Enter name: ");).

Console.ReadLine(): Reads a full line of text entered by the user as a string.

Type Parsing: Console.ReadLine() always returns a string. To convert to an int: int age = int.Parse(Console.ReadLine()); or int age = Convert.ToInt32(Console.ReadLine());.