Steven Giesel

C# Lowering - What is it and why should I care?

The C# compiler turns one `yield` keyword into an entire state machine. Learn how this hidden process impacts your code's performance and memory usage.

C# Lowering - What is it and why should I care?
#1about 7 minutes

Defining C# lowering and its benefits

C# lowering is the process of transforming high-level language features into simpler constructs, which simplifies the compiler and ensures predictable performance.

#2about 3 minutes

Subtle differences in property getter implementations

The `var` keyword is lowered to its inferred type, while expression-bodied properties can introduce subtle behavioral changes compared to traditional getters.

#3about 4 minutes

How `foreach` is lowered for arrays versus lists

A `foreach` loop is lowered to an index-based `while` loop for arrays but uses the `IEnumerable` pattern with a `try-finally` block for lists, impacting performance.

#4about 2 minutes

The danger of using `async` without `await` in `using` blocks

Combining `IDisposable` with an `async` call without `await` can lead to the object being disposed before the asynchronous operation completes.

#5about 9 minutes

Understanding the `yield` keyword and its performance

The `yield` keyword generates a state machine class to enable deferred execution, trading slower per-item runtime for significantly lower memory allocation.

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