Is it possible to use a generic ViewModel with single View?

[Catalan-1ap]

An attempt to use a generic ViewModel leads to an exception, the problem is that the generic ViewModel name contains a generic type name, and ViewManage cannot find my View.

[canton7]

You can, but you'll need to write your own ViewManager which tells Stylet how to find the view which corresponding to a partiuclar ViewModel (with particular generic type arguments)

[Catalan-1ap]

Do I need to write all the ViewManager behavior from scratch? Or can I add a rule for a generic ViewModel?

[Catalan-1ap]

Thanks for the tip. If anyone needs it, here's my implementation.
This ViewManager allows you to use generic ViewModels just like the others.

public sealed class ViewManagerSupportGenericViewModels : ViewManager
{
	private readonly Dictionary<string, Type> _genericViewModelNameWithViewType;


	public ViewManagerSupportGenericViewModels(ViewManagerConfig config) : base(config)
	{
		var allTypes = typeof(Bootstrapper).Assembly
                                                   .GetTypes()
						   .Where(type => type.Name.Contains(ViewNameSuffix,
								  StringComparison.Ordinal))
						   .ToArray();
		var genericViewModels = allTypes
					.Where(type =>
						type.Name.Contains(ViewModelNameSuffix, StringComparison.Ordinal)
						&&
						type.IsGenericType)
					.ToArray();
		var views = allTypes
			    .Except(genericViewModels)
			    .ToArray();

		_genericViewModelNameWithViewType = GetGenericViewModelNameWithViewType(genericViewModels, views);
	}


	protected override Type LocateViewForModel(Type modelType) =>
		modelType.IsGenericType == false
			? base.LocateViewForModel(modelType)
			: _genericViewModelNameWithViewType[modelType.Name];


	private Dictionary<string, Type> GetGenericViewModelNameWithViewType(ICollection<Type> genericViewModels, ICollection<Type> views)
	{
		Dictionary<string, Type> genericViewModelWithViewType = new();

		foreach (var genericViewModel in genericViewModels)
		{
			var nameWithoutGenericInfo = GetTypeNameWithoutGenericInfo(genericViewModel);

			var viewTypeName = ViewTypeNameForModelTypeName(nameWithoutGenericInfo);

			var viewType = views.Single(type => type.Name.Equals(viewTypeName, StringComparison.Ordinal));

			genericViewModelWithViewType.Add(genericViewModel.Name, viewType);
		}

		return genericViewModelWithViewType;
	}


	private static string GetTypeNameWithoutGenericInfo(Type type)
	{
		var tilda = type.Name.IndexOf('`');

		return type.Name[..tilda];
	}
}

[canton7]

Thanks!

Thinking about it more, would it not be easier to override ViewTypeNameForModelTypeName, strip off the stuff after the backtick, then call the base method?

[Catalan-1ap]

You are absolutely right!

Overriding ViewTypeNameForModelTypeName makes the code cleaner, but I doubt the performance.

public sealed class ViewManagerSupportGenericViewModels : ViewManager
{
	private readonly Regex _viewNameForGenericVieModel;


	public ViewManagerSupportGenericViewModels(ViewManagerConfig config) : base(config)
	{
		_viewNameForGenericVieModel = new(
			@$"(<=.)?{Regex.Escape(ViewModelNameSuffix)}(\`.*)?$",
			RegexOptions.Compiled
		);
	}


	protected override string ViewTypeNameForModelTypeName(string modelTypeName) =>
		modelTypeName.Contains('`') == false
			? base.ViewTypeNameForModelTypeName(modelTypeName)
			: _viewNameForGenericVieModel.Replace(modelTypeName, Regex.Escape(ViewNameSuffix));
}

[canton7]

It won't be worse than any other view instantiation. Creating UI elements is expensive, a little bit of reflection is so cheap by comparison that you'll never notice