C#: 𝗧𝗵𝗲 𝗦𝗽𝗲𝗰𝗶𝗳𝗶𝗰𝗮𝘁𝗶𝗼𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻

Karwan Essmat Othman — Tue, 28 Apr 2026 23:02:49 +0000

𝘛𝘩𝘦 𝘚𝘱𝘦𝘤𝘪𝘧𝘪𝘤𝘢𝘵𝘪𝘰𝘯 𝘗𝘢𝘵𝘵𝘦𝘳𝘯 𝘧𝘪𝘹𝘦𝘴 𝘪𝘵: 𝘸𝘳𝘪𝘵𝘦 𝘢 𝘣𝘶𝘴𝘪𝘯𝘦𝘴𝘴 𝘳𝘶𝘭𝘦 𝘰𝘯𝘤𝘦, 𝘶𝘴𝘦 𝘪𝘵 𝘦𝘷𝘦𝘳𝘺𝘸𝘩𝘦𝘳𝘦 — 𝘲𝘶𝘦𝘳𝘪𝘦𝘴, 𝘤𝘰𝘮𝘮𝘢𝘯𝘥𝘴, 𝘷𝘢𝘭𝘪𝘥𝘢𝘵𝘪𝘰𝘯, 𝘵𝘦𝘴𝘵𝘴.

In 8 slides:
✅ Why rules get d̶u̶p̶l̶i̶c̶a̶t̶e̶d̶
✅ Two ways to use a spec 𝙏𝙤𝙀𝙭𝙥𝙧𝙚𝙨𝙨𝙞𝙤𝙣() vs 𝙄𝙨𝙎𝙖𝙩𝙞𝙨𝙛𝙞𝙚𝙙𝘽𝙮()
✅ One e-commerce rule, five real consumers
✅ Combine specs with .𝘼𝙣𝙙() .𝙊𝙧() .𝙉𝙤𝙩()
✅ Test business rules with no database

🪴 𝗣𝗮𝘁𝘁𝗲𝗿𝗻 𝗺𝗮𝘁𝗰𝗵𝗶𝗻𝗴 𝗶𝗻 𝗖# — 𝗰𝗹𝗲𝗮𝗻 𝗰𝗼𝗱𝗲 𝘄𝗶𝘁𝗵 𝗶𝘀, 𝘀𝘄𝗶𝘁𝗰𝗵, 𝗮𝗻𝗱 𝘄𝗵𝗲𝗻 👇

Karwan Essmat Othman — Tue, 28 Apr 2026 22:59:18 +0000

🪴 𝗣𝗮𝘁𝘁𝗲𝗿𝗻 𝗺𝗮𝘁𝗰𝗵𝗶𝗻𝗴 𝗶𝗻 𝗖# — 𝗰𝗹𝗲𝗮𝗻 𝗰𝗼𝗱𝗲 𝘄𝗶𝘁𝗵 𝗶𝘀, 𝘀𝘄𝗶𝘁𝗰𝗵, 𝗮𝗻𝗱 𝘄𝗵𝗲𝗻 👇
𝘚𝘵𝘪𝘭𝘭 𝘸𝘳𝘪𝘵𝘪𝘯𝘨 𝘪𝘧/𝘦𝘭𝘴𝘦 𝘤𝘩𝘢𝘪𝘯𝘴 𝘧𝘰𝘳 𝘵𝘺𝘱𝘦 𝘤𝘩𝘦𝘤𝘬𝘴?

12 lines of if/else → 7 lines with switch expression.
Same logic. Half the code. Easier to read.

3 𝘱𝘢𝘵𝘵𝘦𝘳𝘯𝘴 𝘺𝘰𝘶 𝘴𝘩𝘰𝘶𝘭𝘥 𝘬𝘯𝘰𝘸:
𝗧𝘆𝗽𝗲 𝗽𝗮𝘁𝘁𝗲𝗿𝗻:
𝚒𝚏 (𝚜𝚑𝚊𝚙𝚎 𝚒𝚜 𝙲𝚒𝚛𝚌𝚕𝚎 𝚌)
𝚊𝚛𝚎𝚊 = 𝙼𝚊𝚝𝚑.𝙿𝙸 𝚌.𝚁 𝚌.𝚁;

𝗣𝗿𝗼𝗽𝗲𝗿𝘁𝘆 𝗽𝗮𝘁𝘁𝗲𝗿𝗻:
𝚒𝚏 (𝚘𝚛𝚍𝚎𝚛 𝚒𝚜 { 𝚂𝚝𝚊𝚝𝚞𝚜: "𝙿𝚊𝚒𝚍", 𝚃𝚘𝚝𝚊𝚕: > 𝟷𝟶𝟶 })
𝙰𝚙𝚙𝚕𝚢𝚅𝙸𝙿();

𝗥𝗲𝗹𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗽𝗮𝘁𝘁𝗲𝗿𝗻:
𝚟𝚊𝚛 𝚝𝚒𝚎𝚛 = 𝚜𝚌𝚘𝚛𝚎 𝚜𝚠𝚒𝚝𝚌𝚑 { >= 𝟿𝟶 => "𝙰", >= 𝟾𝟶 => "𝙱", _ => "𝙵" };

𝗧𝗵𝗲 𝗿𝘂𝗹𝗲:
𝙏𝙮𝙥𝙚 𝙘𝙝𝙚𝙘𝙠𝙨? → 𝙞𝙨 + 𝙥𝙖𝙩𝙩𝙚𝙧𝙣
𝟯+ 𝙗𝙧𝙖𝙣𝙘𝙝𝙚𝙨? → 𝙨𝙬𝙞𝙩𝙘𝙝 𝙚𝙭𝙥𝙧𝙚𝙨𝙨𝙞𝙤𝙣
𝙄𝙩'𝙨 𝙖𝙡𝙢𝙤𝙨𝙩 𝙖𝙡𝙬𝙖𝙮𝙨 𝙘𝙡𝙚𝙖𝙣𝙚𝙧.

DEV Community: Karwan Essmat Othman

C#: 𝗧𝗵𝗲 𝗦𝗽𝗲𝗰𝗶𝗳𝗶𝗰𝗮𝘁𝗶𝗼𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻

🪴 𝗣𝗮𝘁𝘁𝗲𝗿𝗻 𝗺𝗮𝘁𝗰𝗵𝗶𝗻𝗴 𝗶𝗻 𝗖# — 𝗰𝗹𝗲𝗮𝗻 𝗰𝗼𝗱𝗲 𝘄𝗶𝘁𝗵 𝗶𝘀, 𝘀𝘄𝗶𝘁𝗰𝗵, 𝗮𝗻𝗱 𝘄𝗵𝗲𝗻 👇