After updating to the latest version of Xamarin forms(18.104.22.1684457 as of writing this) while utilizing version 22.214.171.124 of the Syncfusion Xamarin controls, I began receiving a specified cast is not valid exception when trying to load multiple selected values into a SfComboBox. Specifically I'm seeing this happening on iOS, but I've not tried testing it on Android. I have attached a demo solution that reproduces this behavior, the entire stack trace doesn't seem to fit in this description box but the demo solution is setup in a way that the error is readily reproducable. All that is required is to try and navigate to the Multiple Selection tab and it will reproduce the error. If there is an issue decompressing the 7z file let me know. I had to use some different settings to get the file small enough to pass the 30MB limit.
My dev environment when reproducing this:
Visual Studio Professional 2019 (Version 16.3.1) / Visual Studio For Mac Community (Version 8.3 Build 1805)
Microsoft .NET Framework
Syncfusion Xamarin Project Templates 126.96.36.199
Syncfusion Xamarin Toolbox 188.8.131.52
SyncfusionMenu Extension 1.0
Xamarin 184.108.40.2064 (d16-3@06531f8)
Xamarin Designer 220.127.116.11 (remotes/origin/d16-3-xcode11@bbe518670)
Xamarin Templates 16.3.565 (27e9746)
Xamarin.Android SDK 10.0.0.43 (d16-3/8af1ca8)
Xamarin.Android Reference Assemblies and MSBuild support.
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-3@cb41333
Xamarin.iOS and Xamarin.Mac SDK 18.104.22.168 (5e8a208)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.