AngleSharp by Florian Rappl

<PackageReference Include="AngleSharp" Version="0.8.1" />

.NET API 1,172,480 bytes

CssBorderTopLeftRadiusProperty

sealed class CssBorderTopLeftRadiusProperty : CssBorderRadiusPartProperty, ICssBorderTopLeftRadiusProperty, ICssProperty

Information can be found on MDN: https://developer.mozilla.org/en-US/docs/Web/CSS/border-top-left-radius

public Length HorizontalTopLeft { get; }

public Length VerticalTopLeft { get; }