Format specifiers for numbers and dates in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of numeric format specifier

What is the output of the following C# code snippet?

C Sharp (C#)

double value = 1234.5678;
string result = value.ToString("N2");
Console.WriteLine(result);

A "1234.57"

B "1234.5678"

C "1,234.5678"

D "1,234.57"

💡 Hint

The "N2" format specifier formats the number with commas and 2 decimal places.

The "N2" specifier formats the number with thousands separators and rounds to 2 decimal places, so 1234.5678 becomes "1,234.57".

❓ Predict Output

intermediate

DateTime custom format output

What is the output of this C# code snippet if the date is March 5, 2024, 9:07:03 AM?

C Sharp (C#)

DateTime dt = new DateTime(2024, 3, 5, 9, 7, 3);
string formatted = dt.ToString("yyyy-MM-dd HH:mm:ss");
Console.WriteLine(formatted);

A "2024-03-05 09:07:03"

B "2024/3/5 9:7:3"

C "03/05/2024 09:07:03"

D "5-3-2024 09:07:03 AM"

💡 Hint

The format string uses four-digit year, two-digit month and day, and 24-hour time with leading zeros.

The format string "yyyy-MM-dd HH:mm:ss" produces a date like "2024-03-05 09:07:03" with zero-padded numbers and 24-hour clock.

🔧 Debug

advanced

Identify the error in numeric format string

What error will this C# code produce?

C Sharp (C#)

int number = 255;
string hex = number.ToString("X4Z");
Console.WriteLine(hex);

A Outputs "255"

B Outputs "00FF"

C FormatException at runtime

D Compilation error

💡 Hint

Check if the format string "X4Z" is valid for ToString.

The format string "X4Z" is invalid because "Z" is not a recognized format specifier, causing a FormatException at runtime.

❓ Predict Output

advanced

Output of date format with day and month names

What is the output of this C# code snippet for the date July 20, 2024?

C Sharp (C#)

DateTime dt = new DateTime(2024, 7, 20);
string output = dt.ToString("dddd, MMMM dd, yyyy");
Console.WriteLine(output);

A "07/20/2024"

B "Saturday, July 20, 2024"

C "20/07/2024"

D "Sat, Jul 20, 2024"

💡 Hint

"dddd" gives full day name, "MMMM" full month name.

The format string "dddd, MMMM dd, yyyy" outputs the full day name, full month name, day with leading zero, and four-digit year.

🧠 Conceptual

expert

Understanding composite format strings with numbers and dates

Given the code below, what is the exact output?

C Sharp (C#)

DateTime dt = new DateTime(2024, 12, 31, 23, 59, 59);
int count = 7;
string result = string.Format("Date: {0:MM/dd/yyyy}, Count: {1:D3}", dt, count);
Console.WriteLine(result);

A "Date: 12/31/2024, Count: 007"

B "Date: 31/12/2024, Count: 7"

C "Date: 12-31-2024, Count: 007"

D "Date: 12/31/2024, Count: 7"

💡 Hint

"D3" formats an integer with at least 3 digits, padded with zeros.

The date is formatted as MM/dd/yyyy (month/day/year) and the integer count is formatted as a 3-digit number with leading zeros, so 7 becomes "007".