I've updated to .net preview 9 today and i'm running into an issue with the window components. the TelerikWindow component appears to not have an error, its the child components that appear to be having issues.
I believe the issue is caused by the following change in preview 9.
"Replace Microsoft.AspNetCore.Components.UIEventArgs with System.EventArgs and remove the “UI” prefix from all EventArgs derived types (UIChangeEventArgs -> ChangeEventArgs, etc.)."
Any idea on when the Telerik Blazor components will be updated to support preview 9?