https://learn.microsoft.com/en-us/dotnet/api/system.windows.media.animation.rectkeyframe.system-windows-media-animation-ikeyframe-value?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-9.0
RectKeyFrame.IKeyFrame.Value Property (System.Windows.Media.Animation) | Microsoft Learn
Gets or sets the value associated with a KeyTime instance.
value propertywindows mediasystemanimationmicrosoft