How to add two Hexadecimal numbers?

using System;
using System.Collections.Generic;

class Program
{
    // Map for converting hexadecimal
    // values to decimal
    static Dictionary<char, int> HexValueOfDec()
    {
        // Map the values to decimal values
        Dictionary<char, int> map = new Dictionary<char, int>
        {
            { '0', 0 }, { '1', 1 },
            { '2', 2 }, { '3', 3 },
            { '4', 4 }, { '5', 5 },
            { '6', 6 }, { '7', 7 },
            { '8', 8 }, { '9', 9 },
            { 'A', 10 }, { 'B', 11 },
            { 'C', 12 }, { 'D', 13 },
            { 'E', 14 }, { 'F', 15 }
        };

        return map;
    }

    // Map for converting decimal values
    // to hexadecimal
    static Dictionary<int, char> DecValueOfHex()
    {
        // Map the values to the
        // hexadecimal values
        Dictionary<int, char> map = new Dictionary<int, char>
        {
            { 0, '0' }, { 1, '1' },
            { 2, '2' }, { 3, '3' },
            { 4, '4' }, { 5, '5' },
            { 6, '6' }, { 7, '7' },
            { 8, '8' }, { 9, '9' },
            { 10, 'A' }, { 11, 'B' },
            { 12, 'C' }, { 13, 'D' },
            { 14, 'E' }, { 15, 'F' }
        };

        return map;
    }

    // Function to add the two hexadecimal numbers
    static string AddHex(string a, string b)
    {
        Dictionary<char, int> m = HexValueOfDec();
        Dictionary<int, char> k = DecValueOfHex();

        // Check if length of string first is
        // greater than or equal to string second
        if (a.Length < b.Length)
        {
            string temp = a;
            a = b;
            b = temp;
        }

        // Store length of both strings
        int l1 = a.Length, l2 = b.Length;

        string ans = "";

        // Initialize carry as zero
        int carry = 0, i, j;

        // Traverse till second string
        // get traversal completely
        for (i = l1 - 1, j = l2 - 1; j >= 0; i--, j--)
        {
            // Decimal value of element at a[i]
            // Decimal value of element at b[i]
            int sum = m[a[i]] + m[b[j]] + carry;

            // Hexadecimal value of sum % 16
            // to get addition bit
            char additionBit = k[sum % 16];

            // Add additionBit to answer
            ans = additionBit + ans;

            // Update carry
            carry = sum / 16;
        }

        // Traverse remaining element
        // of string a
        while (i >= 0)
        {
            // Decimal value of element
            // at a[i]
            int sum = m[a[i]] + carry;

            // Hexadecimal value of sum % 16
            // to get addition bit
            char additionBit = k[sum % 16];

            // Add additionBit to answer
            ans = additionBit + ans;

            // Update carry
            carry = sum / 16;
            i--;
        }

        // Check if still carry remains
        if (carry != 0)
        {
            ans = k[carry] + ans;
        }

        return ans;
    }

    // Driver Code
    static void Main(string[] args)
    {
        // Initialize the hexadecimal values
        string str1 = "1B", str2 = "AD";

        // Function call
        Console.WriteLine(AddHex(str1, str2));
    }
}

// This code is contributed by Dwaipayan Bandyopadhyay

using System;

class Program {
    static void Main()
    {
        // Declaring the variables
        string str1 = "1B";
        string str2 = "AD";

        // Calculating hexadecimal value
        int sum = Convert.ToInt32(str1, 16)
                  + Convert.ToInt32(str2, 16);
        string hexSum = sum.ToString(
            "X"); // Convert the sum back to hexadecimal

        // Printing result
        Console.WriteLine(hexSum);
    }
}

using System;

class Program {
    // Function to add two hexadecimal numbers
    static string AddHexadecimal(string a, string b)
    {
        // Convert hexadecimal strings to integers
        ulong intA = Convert.ToUInt64(a, 16);
        ulong intB = Convert.ToUInt64(b, 16);

        // Calculate sum and convert it back to hexadecimal
        ulong sum = intA + intB;
        string result = sum.ToString("X");

        // Return the result as a string
        return result;
    }

    static void Main()
    {
        // Declaring the variables
        string a = "01C";
        string b = "378";

        // Calculating hexadecimal sum
        string hexadecimalSum = AddHexadecimal(a, b);

        // Print the result
        Console.WriteLine(hexadecimalSum);
    }
}