Simple Class to create a well formed HMAC with SHA256 encryption and HEX Encoding

HMACGenerator.cs

using System;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

namespace CajunCoding.HMAC
{
    /// <summary>
    /// BBernard / CajunCoding
    /// A simple class to generate HMAC codes (hash-based message authentication code) to be used for signing and validating
    /// authenticity & integrity of messages between systems. More Info: https://en.wikipedia.org/wiki/HMAC
    /// </summary>
    public static class HMACGenerator
    {
        /// <summary>
        /// Generates a valid HMAC using SHA-256 Encryption with HEX Encoding for transport as a string.
        /// </summary>
        /// <param name="encryptionKey">The shared secret string key used to generate the HMAC.</param>
        /// <param name="value">The value to be hashed.</param>
        /// <returns></returns>
        public static string ComputeSha256HexEncodedHash(string encryptionKey, string value)
        {
            if (string.IsNullOrWhiteSpace(encryptionKey)) throw new ArgumentNullException(nameof(encryptionKey));
            if (string.IsNullOrWhiteSpace(value)) throw new ArgumentNullException(nameof(value));

            var encryptionKeyBytes = Encoding.UTF8.GetBytes(encryptionKey);
            using (var hashAlgorithm = new HMACSHA256(encryptionKeyBytes))
            {
                var valueBytes = Encoding.UTF8.GetBytes(value);
                var hashBytes = hashAlgorithm.ComputeHash(valueBytes);

                var hashString = hashBytes.ToHexString();
                return hashString;
            }
        }

        public static string ToHexString(this byte[] bytes)
        {
            #if NET5_0_OR_GREATER
            return Convert.ToHexString(bytes);
            #else
            return string.Concat(bytes.Select(b => ((int)b).ToString("x2")));
            #endif
        }
    }
}

This is useful for signing and validating authenticity & integrity of messages between systems.

Real World Use Case Example:
When integrating with Intercom to enable Identity verification, they provide a secret signing key and require a well formed HMAC (hash of the User ID or Email) be created with SHA256 encryption & HEX encoding. This class provides the correct implementation for this kind of signing in C#.