CodingSandbox/UserPermissionTest_CS_WinForms/PasswordHasher.cs

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

namespace UserPermissionTest_CS_WinForms
{
    public static class PasswordHasher
    {
        /// <summary>
        /// Hashes the plain-text password using SHA-256.
        /// </summary>
        public static string HashPassword(string password)
        {
            if (password == null) throw new ArgumentNullException(nameof(password));

            using (SHA256 sha256 = SHA256.Create())
            {
                byte[] bytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(password));
                StringBuilder builder = new StringBuilder();
                for (int i = 0; i < bytes.Length; i++)
                {
                    builder.Append(bytes[i].ToString("x2"));
                }
                return builder.ToString();
            }
        }

        /// <summary>
        /// Verifies whether the entered plain-text password matches the stored SHA-256 hash.
        /// </summary>
        public static bool VerifyPassword(string enteredPassword, string storedHash)
        {
            if (enteredPassword == null || storedHash == null) return false;

            string hashedInput = HashPassword(enteredPassword);
            return hashedInput.Equals(storedHash, StringComparison.OrdinalIgnoreCase);
        }
    }
}