Uploaded August 2026 | Updated September 2026, 3 weeks ago

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Everything you're about to see is broken. On purpose.

After weeks of hand-coding the new Avalonia theme engine, we hit the wall every
theming system eventually hits: the old controls don't follow the new rules. So
this episode isn't a clean build — it's the demolition. We rip through the theme,
enforce the one rule that matters (TemplateBinding inside every Control Template,
no exceptions), and watch buttons, spinners, and the calendar control fall apart
in real time. This is what it actually looks like before it gets better.

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📌 WHAT YOU'LL LEARN
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• Why breaking a working system on purpose is sometimes the only path forward
• The one rule you must never break inside a Control Template — and why a plain
Binding instead of TemplateBinding silently blocks every style override forever
• The "horror state" bug: a background stuck red permanently because of a single
wrong binding — and how to spot it before it costs you a day
• What happens when you enforce strict rules retroactively across an entire theme
— the padding issues, the ugly hover states, the fallout
• Why the Calendar control is the worst offender in Avalonia's control set — hard
baked defaults that fight you at every turn
• The real decision point: fix it control-by-control, or rip it out entirely
• Why "very broken" is a normal, necessary stage of a real refactor — not a failure

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⏱ TIMESTAMPS
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0:00 – We've already broken a lot of stuff
1:46 – Where the themes stand right now: very broke
2:48 – The rule: only TemplateBinding inside a Control Template
3:10 – The horror state — stuck red forever
4:35 – Why this makes styling nearly impossible without the rule
5:16 – This turned into a bigger task than expected
5:45 – Nasty hover effects on the Button Spinner
5:58 – The Calendar: not standard, not baked to follow anything
7:05 – Contemplating ripping the Calendar out entirely
8:19 – Current state: obviously very broken (and that's the point)

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🔗 LINKS
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▶ Ep 1 – Setup: youtube.com/watch?v=rUKlQnjU0tc
▶ Ep 2 – Buttons: youtube.com/watch?v=oKjk6pyyARI
▶ Ep 3 – Button Spinner Anatomy: youtube.com/watch?v=WMaTbXkvm9g
▶ Ep 4 – Designing a Theme System: youtube.com/watch?v=I5halHoNfH0
▶ Ep 5 – Checkbox Deep Dive: youtube.com/watch?v=uIimnwjITT0
▶ Ep 6 – Checkbox Styling: youtube.com/watch?v=uv1bNrfCjtY
▶ Ep 7 – Theme Engine From Scratch: youtube.com/watch?v=NXz8hwITg5U
▶ Ep 8 – Design Token System: youtube.com/watch?v=QMVdxRZqaU8
▶ Ep 9 – Surgical Legacy Code Removal: youtube.com/watch?v=5-p_fnOi0As
▶ Ep 10 – One Token System: youtube.com/watch?v=JEcD1XXIiA8
▶ Ep 11 – Styles Not Working? Breaking the Rule: youtube.com/watch?v=OhJN8Ssp2hA

📺 Full Series Playlist: youtube.com/playlist?list=PLrW43fNmjaQVE2vDBeWD8QYIm06w6bKyO
💾 Source Code: github.com/angelsix
🌐 AngelSix: angelsix.com

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📺 SERIES: Avalonia UI Theming – Hand Coded From Scratch
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#avalonia #avaloniaui #xaml #csharp #dotnet #uiux #desktopapp #softwaretutorial #coding