C#: Check a string is Valid Hex Code or not

C# Sharp Regular Expression: Exercise-1 with Solution

Hex color codes start with a pound sign or hashtag (#) and are followed by six letters (A-F) and/or number (digit from 0-9). Alphabetic characters may be uppercase or lowercase.

Write a C# Sharp program to check whether a given string is a valid Hex code or not. Return true if this string is a valid code otherwise false.

Sample Data:
("#CD5C5C") -> True
("#f08080") -> True
("#E9967A") -> True
("#EFFA07A") -> False

Sample Solution-1:

C# Sharp Code:

using System;
using System.Text.RegularExpressions;

namespace exercises
{
    class Program
    {
        // Main method - entry point of the program
        static void Main(string[] args)
        {
            // Initialize a string variable with a hexadecimal color code
            string hc = "#CD5C5C";

            // Display the hexadecimal code
            Console.WriteLine("Hex Code: " + hc);

            // Check if the string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with a new hexadecimal color code
            hc = "#f08080";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with another hexadecimal color code
            hc = "#E9967A";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with another hexadecimal color code (with a mistake)
            hc = "#EFFA07A";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));
        }

        // Method to test if a string represents a valid hexadecimal color code
        public static bool test(string hc)
        {
            // Use Regex to check if the string matches the pattern for a valid hex code
            return Regex.IsMatch(hc, @"[#][0-9A-Fa-f]{6}\b");
        }
    }
}

Sample Output:

Hex Code: #CD5C5C
Check the said string is valid hex code or not: True

Hex Code: #f08080
Check the said string is valid hex code or not: True

Hex Code: #E9967A
Check the said string is valid hex code or not: True

Hex Code: #EFFA07A
Check the said string is valid hex code or not: False

Flowchart:

Sample Solution-2:

C# Sharp Code:

using System;
using System.Text.RegularExpressions;

namespace exercises
{
    class Program
    {
        // Main method - entry point of the program
        static void Main(string[] args)
        {
            // Initialize a string variable with a hexadecimal color code
            string hc = "#CD5C5C";

            // Display the hexadecimal code
            Console.WriteLine("Hex Code: " + hc);

            // Check if the string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with a new hexadecimal color code
            hc = "#f08080";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with another hexadecimal color code
            hc = "#E9967A";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));

            // Update the string variable with another hexadecimal color code (with a mistake)
            hc = "#EFFA07A";

            // Display the new hexadecimal code
            Console.WriteLine("\nHex Code: " + hc);

            // Check if the new string is a valid hex code and display the result
            Console.WriteLine("Check the said string is valid hex code or not: " + test(hc));
        }

        // Method to test if a string represents a valid hexadecimal color code
        public static bool test(string hc)
        {
            // Use Regex to match the string against the pattern for a valid hex code
            // The pattern checks for a '#' followed by exactly 6 characters from 0-9 or a-f (case-insensitive)
            // The "^" and "$" ensure the string matches the entire pattern from start to end
            return Regex.Match(hc, "^#[0-9a-fA-F]{6}$").Success;
        }
    }
}

Sample Output:

Hex Code: #CD5C5C
Check the said string is valid hex code or not: True

Hex Code: #f08080
Check the said string is valid hex code or not: True

Hex Code: #E9967A
Check the said string is valid hex code or not: True

Hex Code: #EFFA07A
Check the said string is valid hex code or not: False

Flowchart:

C# Sharp Code Editor:

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