Apprendre Safe Parsing Techniques | Validating Input and Safe Parsing

When working with user input or data from external sources, you often need to convert, or parse, strings into numbers or dates. This process is called parsing. However, parsing can be risky: if the input is not in the expected format, your program may throw exceptions and crash. For example, trying to convert the string "abc" to an integer using direct parsing will result in a FormatException. To keep your application robust and user-friendly, you need safe parsing techniques that can handle unexpected or invalid input gracefully.

Program.cs


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using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.Write("Enter a number: ");
            string input = Console.ReadLine();

            int result;
            if (int.TryParse(input, out result))
            {
                Console.WriteLine("You entered the number: " + result);
            }
            else
            {
                Console.WriteLine("Invalid input. Please enter a valid integer.");
            }
        }
    }
}

The code above uses the int.TryParse method to safely convert a string to an integer. The TryParse pattern is a safer alternative to direct parsing methods like int.Parse. Instead of throwing an exception when the input is invalid, TryParse returns a boolean value: true if the conversion succeeded, or false if it failed. The parsed value is stored in an output variable only if the conversion is successful. This approach allows you to handle invalid input without risking exceptions or program crashes.

SafeParsingExamples.cs


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// Safe parsing for DateTime and double types (non-runnable example)

string dateInput = "2024-06-10";
DateTime dateValue;
bool isDateValid = DateTime.TryParse(dateInput, out dateValue);

string priceInput = "19.99";
double priceValue;
bool isPriceValid = double.TryParse(priceInput, out priceValue);

// isDateValid and isPriceValid indicate if parsing was successful

This code sample demonstrates how to use the TryParse methods for DateTime and double types to safely validate input and perform parsing without risking exceptions. By checking the boolean result of each TryParse call, you can determine if the input was valid before using the parsed value. This pattern is useful when you need to handle different data types from user or external input. Note that this example is not runnable as it does not include a Main method or an entry point.

1. What is the difference between int.Parse and int.TryParse?

2. Why is `TryParse` preferred for user input?

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Section 3. Chapitre 3

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Program.cs


              123456789101112131415161718192021222324
            
using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.Write("Enter a number: ");
            string input = Console.ReadLine();

            int result;
            if (int.TryParse(input, out result))
            {
                Console.WriteLine("You entered the number: " + result);
            }
            else
            {
                Console.WriteLine("Invalid input. Please enter a valid integer.");
            }
        }
    }
}

SafeParsingExamples.cs


              1234567891011
            
// Safe parsing for DateTime and double types (non-runnable example)

string dateInput = "2024-06-10";
DateTime dateValue;
bool isDateValid = DateTime.TryParse(dateInput, out dateValue);

string priceInput = "19.99";
double priceValue;
bool isPriceValid = double.TryParse(priceInput, out priceValue);

// isDateValid and isPriceValid indicate if parsing was successful

1. What is the difference between int.Parse and int.TryParse?

2. Why is `TryParse` preferred for user input?

Tout était clair ?

Merci pour vos commentaires !

Section 3. Chapitre 3

Safe Parsing Techniques

1. What is the difference between int.Parse and int.TryParse?

2. Why is TryParse preferred for user input?

Safe Parsing Techniques

1. What is the difference between int.Parse and int.TryParse?

2. Why is TryParse preferred for user input?

2. Why is `TryParse` preferred for user input?

2. Why is `TryParse` preferred for user input?