Polyfills (Legacy TFM Support)

Enable modern C# features on older target frameworks.

Enabling Polyfills

Add to your project file:

<PropertyGroup>
  <InjectANcpLuaLanguageFeaturesPolyfills>true</InjectANcpLuaLanguageFeaturesPolyfills>
</PropertyGroup>

Available Polyfills

Feature	TFM Range	What It Enables
Records	< net5.0	record keyword
Index/Range	< netcoreapp3.1	arr[^1], arr[1..3]
Required Members	< net7.0	required keyword
System.Threading.Lock	< net9.0	New Lock type
TimeProvider	< net8.0	Testable time abstraction
Init-only Setters	< net5.0	init keyword
Nullable Attributes	< netstandard2.1	[NotNull], [MaybeNull]
CallerArgumentExpression	< net6.0	Better exception messages

Example: Records on netstandard2.0

// Works on netstandard2.0 with polyfills enabled
public record Person(string Name, int Age);

var person = new Person("Alice", 30);
var older = person with { Age = 31 };

Example: Index/Range on net48

// Works on .NET Framework 4.8 with polyfills enabled
var array = new[] { 1, 2, 3, 4, 5 };

var last = array[^1];           // 5
var slice = array[1..3];        // [2, 3]
var lastTwo = array[^2..];      // [4, 5]

Example: TimeProvider on net6.0

// Works on .NET 6.0 with polyfills enabled
public class MyService(TimeProvider time)
{
    public bool IsExpired(DateTimeOffset expiry)
    {
        return time.GetUtcNow() > expiry;
    }
}

Guard Clauses

Guard clauses are enabled by default (no property needed):

// Available on all target frameworks
public void Process(string name, object data)
{
    Throw.IfNullOrEmpty(name);    // with CallerArgumentExpression
    Throw.IfNull(data);
}

Polyfill Properties

Property	Default	Description
InjectANcpLuaLanguageFeaturesPolyfills	false	Enable all language polyfills
InjectANcpLuaIndexRangePolyfills	false	Enable only Index/Range
InjectANcpLuaGuardClauses	true	Enable Throw.* guard clauses