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Activity 1.7 Prompting for Numerical Input

Introduction

In the last activity, we learned how to prompt a user for input, and save their response to a variable. There is an issue that may arise with using Console.ReadLine(), this method always returns a string. Math cannot be performed with strings. Therefore, we need to be able to convert strings containing numbers into the number data type.

There are two methods for converting a string into a number:

Examples

Convert.ToInt32("32") // "32" converts to 32
Convert.ToDouble("100.4") // "100.4" converts to 100.4
Convert.ToInt32("32.5") // Raises an error. C# doesn't want to corrupt the data by removing the decimal.

Skills to Practice

Instructions

Setup

  1. Create a new C# console application. Name the project 1.7 Numerical Input.
  2. Click Create.

Code

// Age to months calculator
Console.WriteLine("--- Age to Months Calculator ---");
// Steps involved in the statements below:
// 1) User types in age
// 2) Convert string input to integer and save it to a new variable
Console.Write("Enter your age: ");
string ageString = Console.ReadLine();
int age = Convert.ToInt32(ageString);

Console.WriteLine($"You are {age} years old. That's {age * 12} months old, you old fart!\n");

// Square area calculator
Console.WriteLine("--- Square Area Calculator ---");
// Shorter, concise way to get input, convert to number, and save to variable
Console.Write("Enter the length of the square: ");
double length = Convert.ToDouble(Console.ReadLine());
Console.Write("Enter the unit of measurement (in, ft, m): ");
string unit = Console.ReadLine();
double area = length * length;

Console.WriteLine($"The area of the square is {area}{unit} squared");

Debug

--- Age to Months Calculator ---
Enter your age: 30
You are 30 years old. That's 360 months old, you old fart!

--- Square Area Calculator ---
Enter the length of the square: 25.5
Enter the unit of measurement (in, ft, m): ft
The area of the square is 650.25ft squared

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