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DependentHandle Impacts Performance

01/11/2026

DependentHandle is a special type of handle provided by the .NET Garbage Collector (GC).

This handle creates a dependency between the lifetime of two objects. It has a 'weak' reference to a target object and a reference to a dependent object. The weak reference to the target object means that a dependent handle does not extend the lifetime of this target object. The reference to the dependent object remains live as long as the target object is live.

Use-Case

A common use case for DependentHandle is when you need to associate additional fields with an object without extending its lifetime through a strong reference. While this type is not commonly used in typical line-of-business (LOB) applications, it is a handy tool for debuggers, profilers, and other diagnostic or development-time features. A special ConditionalWeakTable also exists, allowing a collection of DependentHandles to be stored in memory.

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Params ReadOnlySpan

12/28/2025

I have recently come across a method in C# that is best resembled by the following method:

public int Sum(IEnumerable<int> values)
{
    int sum = 0;
    foreach (var value in values)
        sum += value;
    return sum;
}

The actual method body looks different, the signature of the method is identical. This method is invoked at 30-40 callsites, and the majority of callsites look like:

Sum([1]);
// or
Sum([1, 2]);
// or
Sum([1, 2, 3]);

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Division in Assembly

12/12/2025

HTTP/3 specification reserves a range of identifiers for streams and frame types. The range as 0x1f * N + 0x21 for non-negative integer values of N.

A received identifier should be validated against the reserved range. This involves subtrackting 33 and then validating if the result is a multiple of 31. The number 31 holds special importance in this context as it is represented by 2N - 1, or 0x0001_1111. This property influences the approaches used for validation.

Several strategies were considered to verify whether a value is a multiple of 31:

• bit manipulation (summing every 5 bits) value to check if the sum is a multiple of 31.

• lookup table

• using divrem Input % 31 == 0

• using integer division and multiplication (Input / 31) * 31 == Input

• multiplication and bit shifting (divide by 2).

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Task over ValueTask<>

11/09/2025

I recently ran into some code that extensively used ValueTask types along with Task. I became curious if it is a good idea to mix async ValueTask<>s and Tasks. Moreover, .NET allows decorating methods returning ValueTask<> types with [AsyncMethodBuilder(typeof(PoolingAsyncValueTaskMethodBuilder<>))] that adds pooling behavior, which reduces allocations.

There are many ways to invoke async methods from another async method. The invoked async method can return a Task, ValueTask<>, or a pooled ValueTask<>; the calling method can also return any of these response types, and be a sync or async method. In this post, I create combinations of these methods to measure their performance footprint. The inner method may complete synchronously, asynchronously, or with a probability set between 0..1, where 1 means synchronous completion.

In this blog post, 'sync' completion refers to returning the result of an underlying async method without awaiting it, or without .Result / .GetAwaiter().GetResult() calls. It does not refer to the 'sync-over-async' anti-pattern.

I used BenchmarkDotNet to measure the performance and allocations of these method combinations. Please note that the allocations show 'non-round' numbers due to BenchmarkDotNet's aggregation when the probability falls between 0 and 1 exclusively. Async completions invoke Task.Yield(); - which yields execution of the current task, allowing other tasks to execute. While there should be no other tasks running in the benchmark, the Mean performance results include a non-trivial waiting duration, that is for the task continuation to execute.

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Async Task Closures

10/26/2025

In .NET async methods get compiled to an async state machine. When awaiting a method call returning a Task the state of the current method is captured by a compiler generated value type, that also implements IAsyncStateMachine.

In this blog post I use .NET 9 to explore some internals of this behavior.

Capturing Structs

I have recently encountered one such async method in production code. The method received a few input parameters, created a struct instance populating its properties with the input parameters. Then serialized the struct instance to string and sent an HTTP POST request using HttpClient while awaiting the result.

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