Polyfills

When targeting netstandard2.0, the SDK injects polyfills for modern C# features.

Feature	What it enables
`Index` / `Range`	`array[^1]`, `array[1..3]` syntax
`IsExternalInit`	`record` types and `init` properties
Nullability attributes	`[NotNull]`, `[MaybeNull]`, etc.
`TimeProvider`	Testable time abstraction
Trim/AOT attributes	`[RequiresUnreferencedCode]`, etc.
String extensions	`string.Contains(char)` overloads

Opt-in Polyfills

Additional polyfills available on request:

<PropertyGroup>
  <InjectLockPolyfill>true</InjectLockPolyfill>
  <InjectTimeProviderPolyfill>true</InjectTimeProviderPolyfill>
</PropertyGroup>

Polyfills are only injected for netstandard2.0 / netstandard2.1 targets. .NET 10 projects don’t need them.

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