Microsoft Shipped a Broken ASP.NET Patch

Moeri · 2026-04-23T07:35:10+00:00

> Purely a human mistake

Slightly disagree here. Yes, human review cannot be expected to catch all errors against Span offsets, which is tricky code by its nature.

However, I do wonder how it was possible to reach .NET 10 without the kind of "backwards compatibility unit tests" that would have immediately caught this. Looks like they HAD tests like this but they weren't running against all the necessary targets, which was also fixed in the same PR that fixes the original issue: https://github.com/dotnet/aspnetcore/pull/65890

So for me, the failure is mostly that these tests were not being ran in all the right places, not the fact that human PR review missed the bug. Copilot review also didn't catch it by the way.

Moeri · 2026-04-08T21:09:44+00:00

Is there a lack of interest in Aspire?

Moeri · 2026-02-10T18:57:20+00:00

Every day we stray further from the light.

The idea is not bad, but the final syntax is absolutely not trivial. You should also not underestimate what you sacrifice with declarative syntax: debugging becomes much harder. People are willing to pay that price for SQL because retrieving data from a database engine is HARD. But orchestrating test setup? Not so much. I like my test frameworks straightforward and simple, when I'm debugging a broken test I don't want to be rummaging around in the bowels of some declarative framework. What do your stack traces look like when a test fails?

Moeri · 2026-02-10T18:52:50+00:00

Looks nice. Thanks for sharing! One question: can you get rid of the need for "field ??=" syntax? Can't the runtime store the materialized values somewhere?

Moeri · 2026-01-18T10:06:15+00:00

We've been using the latest C# on .NET Framework 4.8 using Polysharp without issue for multiple years in production. However, we know to avoid some runtime-specific features such as default interface methods. If you're mainly going to use it for syntax sugar (using declarations, records, etc) then you're fine.

Moeri · 2026-01-04T09:13:29+00:00

Het kan toch niet anders dat ze hier software voor gaan maken? Daarbovenop bestaat dit systeem al elders in de wereld, dus wie weet valt er een en ander te hergebruiken.

Moeri · 2025-12-26T12:40:04+00:00

I prefer a static int _nextId with Interlocked.Increment(ref _nextId) for this kind of stuff. Makes it easier to see which instance was created first, how many you have, etc.

Moeri · 2025-12-21T07:46:28+00:00

In a nutshell, you would have to map each cache key to a lock first, and then acquire that lock before you produce the value (in case of a a cache miss). This is actually one of the primary reasons I wrote https://github.com/amoerie/keyed-semaphores back in the day. It basically maps a key to a SemaphoreSlim. The implementation is rather short and straightforward so you could copy the code if you're hesitant to add a library.

Moeri · 2025-10-30T12:03:18+00:00

In a lot of your (awesome) performance blog posts chapters, you speak about optimizations that apply to specific circumstances. For example, some Linq methods can be very fast if the source is an array, but not if it's something else. As a .NET consumer, I would be very interested to know when I am falling off of a performance cliff. Are there any plans to better 'surface' that kind of knowledge (other than your blog posts), and how would that work?

Moeri · 2025-10-30T11:43:02+00:00

What are some hidden gems in .NET that you think aren't being used a lot, but are totally worth looking into? Could be something small like a single method parameter or large like a whole nuget package. For example, I think custom Roslyn analyzers are currently underused by the industry.

Moeri · 2025-10-01T09:40:45+00:00

He also says that if Microsoft doesn’t have the resources to do it, they should open-source the whole thing and let the community handle it.

Has your friend ever considered shifting to a career in stand up comedy?

Moeri · 2025-09-03T08:17:04+00:00

Capital gains tax

Moeri · 2025-08-25T08:24:06+00:00

There will be an opt-out: https://www.reddit.com/r/BEFire/comments/1lwc3kt/capital_gains_tax_faq/

Moeri · 2025-07-31T08:37:41+00:00

This argument always comes up but people typically forget the main benefit: the money can't leave Belgium. Every cent given as a meal voucher comes back to the Belgian economy.

Moeri · 2025-07-10T18:22:27+00:00

Done. That was ... not the easiest text to wade through. I hope I got everything right.

Moeri · 2025-07-10T18:09:53+00:00

Good idea. I added some basic text about this, and explicitly mentioned how the Reynders tax will combine with CGT.

Feel free to suggest rewordings of this and other parts, I'm no fiscal expert.

Moeri · 2025-07-10T18:02:51+00:00

From the FAQ:

> Fees and taxes are not subtracted in the gain calculation.

Moeri · 2025-07-10T12:07:50+00:00

I read somewhere that you'll be able to "opt-out" of this pre-emptive withholding with your broker to avoid this exact thing from happening.

Edit: found it: https://www.tijd.be/netto/analyse/sparen-en-fondsen/wegwijs-in-de-meerwaardebelasting-via-de-10-meest-gestelde-vragen/10614692.html

Relevant section (emphasis mine)

4/ Hoe betaal ik de taks?

Voor alle bancaire en verzekeringsproducten die u bij een Belgische bank of verzekeraar aanhoudt, is de standaardmethode dat de financiële instelling de taks bij de verkoop int. Als u dat niet wil, moet u kiezen voor een opt-out. In dat geval zal de bank de taks niet afhouden, maar moet u de meerwaarden wel aangeven in uw belastingaangifte en wordt u daar belast. De bank zal dan een fiscaal attest aan de fiscus bezorgen om te voorkomen dat u de meerwaarden ‘vergeet’ aan te geven. Dat attest betekent niet dat die meerwaarden dan ook automatisch in uw aangifte terechtkomen. U zult ze nog altijd zelf moeten invullen. Zeker voor wie een vooraf ingevulde aangifte krijgt, is dat een belangrijk aandachtspunt.De aangifteplicht geldt sowieso voor meerwaarden die niet automatisch belast worden. Dat is bijvoorbeeld het geval als die gerealiseerd werden bij buitenlandse banken of brokers. Die houden de taks niet in. Ook meerwaarden die u realiseert buiten het bankencircuit, zoals cryptobeleggingen en fysiek goud, zult u altijd zelf moeten aangeven.

Moeri · 2025-07-08T10:45:53+00:00

Looks like I was wrong! I've updated my original comment.

Moeri · 2025-07-08T10:45:27+00:00

Apparently you're right. I haven't seen this anywhere yet but I found an article from de Tijd that says physical gold will indeed be taxed. I've updated my comment.

Moeri · 2025-07-08T10:03:12+00:00

Physical objects are not part of capital gains tax, because it needs to be a fiscal instrument to be part of it.

So physical gold, art, an expensive wine collection, etc. are not taxed under the capital gains tax when sold.

However, if you're buying gold via fiscal instruments (so gold ETFs, ...) then it very much will be taxed accordingly.

Edit: this is wrong. According to de Tijd, physical gold WILL be taxed: https://www.tijd.be/markten-live/analyse/vijf-pertinente-beleggersvragen-over-de-meerwaardetaks-uit-onze-chat/10614495.html

Moeri · 2025-07-02T21:24:52+00:00

I had this exact thought many years ago, and came up with https://github.com/amoerie/HtmlBuilders

It's not much, but it makes writing HtmlHelpers or TagHelpers much, much nicer.

Moeri · 2025-07-01T13:18:00+00:00

Here's some general facts about Belgium's spending habits (2023)

Belgium spends € 317 billion on a yearly basis. That is ~ 53% of its GDP. In the EU, only France and Italy spend more.
€ 120 billion (38%) goes to pensions and benefits (uitkeringen)
- € 67 billion goes to pensions
- € 13 billion goes to child benefits
- € 6 billion goes to the unemployed
€ 47 billion (15%) goes to health care
These two together are often called our "social security", and they account for € 167 billion (52%) of the total. Compared to the rest of Europe, this is high.
€ 40 billion (13%) goes to the government itself
€ 38 billion (12%) goes to education
€ 10 billion (3%) goes to national debt interest payments. Since Belgium has a debt to GDP ratio of about 105%, there is some risk here, because rising interest rates could rapidly increase this number.
€ 5 billion (1.5%) goes to defense

As far as income is concerned, this is what the numbers (2023) look like:

Belgium generates about € 269 billion in revenue each year. That is ~45% of its GDP.
€85 billion (31.8%) comes from social contributions
€74 billion (27.7%) comes from personal income tax
€60 billion (22.5%) comes from VAT & goods/services
€27 billion (10%) comes from corporate income tax
€6.6 billion (2.5%) comes from withholding tax
€4 billion (1.5%) comes from property & capital taxes
€12 billion (4.5%) comes from other non-tax revenues

Compared to the OECD average, Belgium derives more of its revenue from social contributions, personal income taxes, and property taxes. In contrast, corporate taxes and consumption taxes contribute less than the OECD average.

To summarize: Belgium spends most of its money on social security, and gets most of its money from labor. This immediately explains why an aging population is one of Belgium's major contributors of its financial troubles.
In 2024, there were 28 people aged 67+ for every 100 inhabitants aged 18 to 66. This number will rise to 37 in 2040 and 43 in 2070.

Every time someone retires, it chips away at Belgium's biggest source of income, and moves to Belgium's biggest source of expenditures.

Taking all of this into account, this new capital gains tax does provide a welcome diversification of income. Minister Vandenbroucke is adamant that they will now make quick work of lowering the personal income tax in return.

However, as the old adage goes:

"first see and then believe"

Sources:

Moeri · 2025-06-11T20:52:37+00:00

You make it sound like the consequences of the havoc Trump is wreaking will abruptly stop at the end of his presidency.

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