Parsing input to numeric types in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of parsing valid and invalid numeric strings

What is the output of the following C# code?

C Sharp (C#)

using System;
class Program {
  static void Main() {
    string input1 = "123";
    string input2 = "12.3";
    int result1 = int.Parse(input1);
    try {
      int result2 = int.Parse(input2);
      Console.WriteLine(result2);
    } catch (FormatException) {
      Console.WriteLine("FormatException caught");
    }
    Console.WriteLine(result1);
  }
}

A

123
FormatException caught

B

12
123

C

FormatException caught
123

D

FormatException caught
12

💡 Hint

int.Parse expects a string that represents a whole number without decimals.

The string "123" parses correctly to int 123. The string "12.3" is not a valid integer format, so int.Parse throws a FormatException, which is caught and prints the message. Then the first parsed integer 123 is printed.

❓ Predict Output

intermediate

Parsing float with TryParse and output

What will be the output of this C# code?

C Sharp (C#)

using System;
class Program {
  static void Main() {
    string input = "3.14";
    if (float.TryParse(input, out float value)) {
      Console.WriteLine(value);
    } else {
      Console.WriteLine("Failed to parse");
    }
  }
}

A 3.14

B Failed to parse

C 3,14

D 0

💡 Hint

TryParse returns true if parsing succeeds and outputs the parsed value.

The string "3.14" is a valid float representation in C# when using the invariant culture or default culture with dot decimal separator, so TryParse returns true and prints 3.14.

🔧 Debug

advanced

Why does parsing "-123" to uint fail?

Consider this code snippet: uint number = uint.Parse("-123"); What error will this code produce when run?

A System.OverflowException

B System.FormatException

C System.ArgumentNullException

D No error, number = 4294967173

💡 Hint

uint cannot represent negative numbers.

Parsing "-123" to uint causes an OverflowException because uint only accepts values from 0 to 4,294,967,295. Negative values are out of range.

📝 Syntax

advanced

Identify the syntax error in parsing code

Which option contains a syntax error in parsing a string to int?

A int.TryParse("100", out int result)

B int.Parse("100";

C int.TryParse("100", out result)

D int.Parse("100")

💡 Hint

Check for missing or extra characters in method calls.

Option B is missing a closing parenthesis and semicolon is misplaced, causing a syntax error.

🚀 Application

expert

Result of parsing multiple inputs with culture-specific decimal separator

Given this code snippet: using System; using System.Globalization; class Program { static void Main() { string input1 = "1234,56"; string input2 = "1234.56"; var culture = new CultureInfo("fr-FR"); if (double.TryParse(input1, NumberStyles.Any, culture, out double val1)) { Console.WriteLine(val1); } else { Console.WriteLine("Failed input1"); } if (double.TryParse(input2, NumberStyles.Any, culture, out double val2)) { Console.WriteLine(val2); } else { Console.WriteLine("Failed input2"); } } }

A

Failed input1
Failed input2

B

Failed input1
1234.56

C

1234,56
1234.56

D

1234.56
Failed input2

💡 Hint

The French culture uses comma as decimal separator, not dot.

In "fr-FR" culture, "1234,56" parses correctly as 1234.56 double value. "1234.56" fails because dot is not a valid decimal separator in French culture.