Ok, figured it out. The Radzen IDE isn't properly handling C# "forward declarations" for classes used with RadzenDropDown components used in a data binding.
namespace DeviceUi2.Pages
{
public partial class TimeSettingsComponent : IDisposable { }
public partial class FMUTimeSettings
{
public TimeSettingsComponent parent { get; set; }
public string timeZone { get; set; }
public List<string> timeZones { get; set; } = null;
...........
public partial class TimeSettingsComponent : IDisposable {
........more code here
}
I am refactoring this code, as it's pretty bad, but there is a "parent" property that is holding the parent object of this class that is used internally by the class. This code will compile and run fine in VS or Radzen, but the visual editor has the "The type or namespace name 'IReadOnlyRadzenDictionary<,> could not be found" is displayed instead of the dropdown box. The app executes fine, and the dropdown works and is displayed correctly. It's in the editor display is where I see the error message.
If I comment out the "public TimeSettingsComponent parent { get; set; }" property, the dropdown is correctly displayed in the radzen editor. Or, if I clear the Data property from the dropdown, it is displayed correctly in the editor also. The Data property for the dropdown is set to the "timeZones" property in this class. The Value is set to the "timeZone" property.
I also do a lot of C++ still and I realize this isn't a real "fowards declaration". Plus, I'm gonna rework this code to get rid of the parent. But I guess having multiple C# partial class blocks really is difficult to handle in the Radzen editor parser?
Thanks!