Application.Current.Resources no keys available

Description

Hello, everyone,

I tried to load a style from code, unfortunately the ResourceDictionary shows me that it has 35 objects but no single key or value.

I don’t know if I’m doing something wrong, but I can’t load a style with a key

Steps to Reproduce

1. Create Maui App
2. Add Button in MainPage
3. Add code

    private void Button_Clicked(object sender, EventArgs e)
    {
		var res = Application.Current.Resources.MergedDictionaries.FirstOrDefault() as ResourceDictionary;

		if(res.ContainsKey("Primary"))
                {
        
                }
    }

Version with bug

6.0 (current)

Last version that worked well

Unknown/Other

Affected platforms

Android, I was not able test on other platforms

Affected platform versions

Android API 31

Did you find any workaround?

No response

Relevant log output

No response

[StephaneDelcroix]

you can’t enumerate the resources (design choice at the time, for reasons I can’t recall at the moment), but you can query it using TryGetValue()

the main purpose of ResourceDictionary is to be the source for {StaticResource}

[breenbob]

From inspecting the resource dictionary a bit more closely, I could see that under the Private properties there is a property called MergedResources which looks to be populated appropriately:

So as a workaround, I’ve written an extension method to find a resource from this. It’s not ideal, and not going to be very efficient as it uses reflection on every call to it, so I will be removing this workaround from my own code as soon as this issue is fixed in Maui, but at least it works.

public static object FindResource(this ResourceDictionary mainResourceDictionary, string resourceKey)
{
        var mergedResources = mainResourceDictionary
            .GetType()
            .GetProperty("MergedResources", BindingFlags.Instance | BindingFlags.NonPublic)
            .GetValue(mainResourceDictionary);

        var dict = ((IEnumerable<KeyValuePair<string, object>>)mergedResources)
            .ToDictionary(x => x.Key, y => y.Value);

        if (dict?.ContainsKey(resourceKey) == true)
        {
            return dict[resourceKey];
        }

        return null;
}

The reason for Casting to an IEnumerable<KeyValuePair<string, object>> is that casting to a Maui.Controls.ResourceDictionary throws an exception for some reason. The actual type of the underlying implementation property was an IEnumerable<KeyValuePair<string, object>>:

Usage: myView.Style = Application.Current.Resources.FindResource("StyleKey") as Style;

Control now getting Style object:

Disclaimer - I’ve only tried this on Windows, but Op has said it also affects Android. The Microsoft.Maui.Controls.ResourceDictionary class implements a bunch of other collection type interfaces, so would be cautious about whether other platforms store the data in different collection types.