README.md

Input Validation (C#)

This module teaches defensive input handling for interactive programs.

Learning Metadata

• Difficulty: Intermediate.
• Estimated Time: 30-45 minutes.
• Prerequisites: 01-foundations/control-flow, 01-foundations/types-and-io.
• Cross-Language Lens: Compare loop-driven validation in all four languages and notice where parsing APIs are strict versus forgiving.

Quick Run

dotnet run --project example/input-validation-example.csproj

Topics Covered

• Validating integers and decimals using TryParse.
• Enforcing value ranges before consuming input.
• Reusing helper methods for consistent validation logic.
• Keeping console applications stable when users provide invalid data.

Common Pitfalls

• Using int.Parse or double.Parse directly for user-entered text.
• Accepting out-of-range values after successful parsing.
• Duplicating similar validation loops instead of extracting helpers.

Exercise Focus

• exercises/01.cs: read an integer in range 1 to 100 and print its square.
• exercises/02.cs: read a valid score count and valid scores, then print average.

Exercise Specs

1. exercises/01.cs

• Input: repeated attempts until a valid integer in range 1..100 is entered.
• Output: square of the accepted value.
• Edge cases: non-numeric text; values below 1 or above 100.

2. exercises/02.cs

• Input: score count in range 1..50, followed by scores in range 0..100.
• Output: average score.
• Edge cases: invalid score entered mid-sequence; boundary values 0 and 100.

Checkpoint

• I can validate input with TryParse and range checks.
• I can recover from invalid entries without terminating the program.
• I can structure reusable input helper methods.
• I completed exercises/01.cs.
• I completed exercises/02.cs.