The protocol layer is multi target-.NET Framework and. NET Core components live, and it runs in a separate. The client layer is part of Visual Studio and it targets the classic. The design-time is separated into three layers-client, protocol and server. Still at its core the chosen solution has not changed much since. Back then it missed a lot of features and it lacked extension points and API to allow custom designers. Microsoft released the first preview of the WinForms designer a little over one year ago. As you cannot interact with the components, you need new solution hence the new architecture. NET Framework and inside the Visual Studio process- devenv.exe, you cannot access. Visual Studio is a desktop application built on top the. NET Framework controls, it will not work with. NET Core components simply because Visual Studio relied on interacting directly with the components that were being designed. NET Core controls in the Visual Studio design surface, you come to understand how complex this really is. The simple answer is-we need new designers because the underlying architecture has changed. This question has been around for a while. NET 5.0 is official, we have the time to speak in more details about our support for the Visual Studio WinForms design-time in. We released them in R3 2020 which was in mid-September. NET Core Telerik WinForms designers have been around for a while.