Hi Lance, I've worked with your suggestions and had no luck, so I decided to start a fresh project and figure out at what point the project actually breaks. It is when I change the target version of Windows to version 1809 in the UWP project. After that, I get a run-time error with any RadButton.
Steps to re-create:
1) Started a new project with the normal Xamarin template (NOTE: I did NOT use the telerik template, as I need to be on .NET Standard 2.0 and not .NET Framework x.x.x
2) I installed latest Telerik UI for Xamarin (2019.1.318.1)
3) Added two lines of code into the Common code's MainPage.xaml to get this:
<?xml version="1.0" encoding="utf-8" ?>
<!-- Place new controls here -->
<Label Text="Welcome to Xamarin.Forms!"
<telerikInput:RadButton Text="RadButton Test"/>
So far, so good. All worked.
4) Upgraded Xamarin.Forms all the way to it's Latest stable version (220.127.116.114807) across entire platform .. still all good.
5) Upgraded Microsoft.NetCore.UniversalWindowsPlatform from the version it was on from the template (6.1.?) to 6.2.8 .. still all good.
6) Like my other project, I installed SkiaSharp.Svg version 1.60.0 for App1.csproj only. Still RadButton worked fine.
7) Changed the target version of App1.UWP.csproj from Win10 16299 to version 1809 (build 17763).
This is where I receive the run-time error during what appears to be the InitializeComponent() method in MainPage.xaml.cs
8) To further isolate the issue, I removed the SkiaSharp.Svg nuget. Same problem exists, so it has to be because I'm targeting 1809.
9) I noticed Telerik UI was still using SkiaSharp version 1.59.3 as a dependency, so as a further test, I installed SkiaSharp version 1.68.0 directly into every project. Same issue.
10) I noticed that under Telerik UI, SkiaSharp was using 1.68.0 but SkiaSharp.Views.Forms was still 1.59.3, so I installed SkiaSharp.Views nuget version 1.68.0 also. I received a warning that it was restored using .NET Framework 4.6.3 instead of .NET Core and may not be compatible. I noticed Telerik UI still listed SkiaSharp.Views.Forms as 1.59.3 after this. Screenshot attached. No luck when running.
11) I downgraded the Windows 10 Target Version to 1803. It worked as expected.
As a final test, I started another project using Telerik's Xamarin template, checked, it was targeting 1809 by default. I built and ran, everything worked fine. I replaced the default label with this RadButton: <telerikInput:RadButton Text="RadButton Test"/>
in to the portable code's MainPage.xaml and did nothing else. Project built and had the same run-time error.
I believe this strips the problem down to it's essence. It is definitely a problem with something inside RadButton when targeting version 1809.