C#: Check whether a string represents a currency value

Last update on August 25 2025 12:53:04 (UTC/GMT +8 hours)

Write a C# Sharp program to check whether a given string represents a currency value or has the correct format to represent a currency value.

Sample Solution:

C# Sharp Code:

using System;
using System.Globalization;
using System.Text.RegularExpressions;

public class Example
{
    public static void Main()
    {
        // Get the current NumberFormatInfo object to build the regular 
        // expression pattern dynamically.
        NumberFormatInfo nfi = NumberFormatInfo.CurrentInfo;

        // Define the regular expression pattern.
        string pattern;
        pattern = @"^\s*[";

        // Get the positive and negative sign symbols.
        pattern += Regex.Escape(nfi.PositiveSign + nfi.NegativeSign) + @"]?\s?";

        // Get the currency symbol.
        pattern += Regex.Escape(nfi.CurrencySymbol) + @"?\s?";

        // Add integral digits to the pattern.
        pattern += @"(\d*";

        // Add the decimal separator.
        pattern += Regex.Escape(nfi.CurrencyDecimalSeparator) + "?";

        // Add the fractional digits.
        pattern += @"\d{";

        // Determine the number of fractional digits in currency values.
        pattern += nfi.CurrencyDecimalDigits.ToString() + "}?){1}$";

        // Create a Regex object with the generated pattern.
        Regex rgx = new Regex(pattern);

        // Define some test strings.
        string[] tests = { "-42", "19.99", "0.001", "100 USD",
                         ".34", "0.34", "1,052.21", "$10.62",
                         "+1.43", "-$0.23" };

        // Check each test string against the regular expression.
        foreach (string test in tests)
        {
            if (rgx.IsMatch(test))
                Console.WriteLine("{0} is a currency value.", test);
            else
                Console.WriteLine("{0} is not a currency value.", test);
        }
    }
}

Sample Output:

-42 is a currency value.
19.99 is a currency value.
0.001 is not a currency value.
100 USD is not a currency value.
.34 is a currency value.
0.34 is a currency value.
1,052.21 is not a currency value.
$10.62 is a currency value.
+1.43 is a currency value.
-$0.23 is a currency value.

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