WPF vs WinForms
Reference a .NET Core Library in WinForms Application
Try to use the DotCoolControls
Open Source WinForms
OpenWinForms is a open source website for windows forms and controls. Here you can find windows controls and libraries for free. This is a non-commercial open source web site. This site mainly focuses on Microsoft technologies e.g. Microsoft .net, VB.net, C#.net etc. You may use these for any commercial or non-commercial purpose for free, however you cannot sell them directly or by modifying.