[Proposal] ImageResourceConverter

ImageResourceConverter

• Proposed
• Prototype
• Implementation
  • iOS Support
  • Android Support
  • macOS Support
  • Windows Support
• Unit Tests
• Sample
• Documentation

Summary

Converts embedded image resource ID to it ImageSource

Detailed Design

ImageResourceConverter.shared.cs

public class ImageResourceConverter : IValueConverter
{
  public object? Convert(object? value, Type? targetType, object? parameter, CultureInfo? culture)
  {
	if (value == null)
		return null;

	if (value is not string imageId)
		throw new ArgumentException("Value is not a string", nameof(value));

	return ImageSource.FromResource(imageId, Application.Current.GetType().GetTypeInfo().Assembly);
  }

  public object ConvertBack(object? value, Type? targetType, object? parameter, CultureInfo? culture) => throw new NotImplementedException();
}

Usage Syntax

XAML Usage

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
             xmlns:myEnum="MyLittleApp.Models"
             x:Class="MyLittleApp.MainPage">

    <ContentPage.Resources>
        <ResourceDictionary>
            <xct: ImageResourceConverter x:Key="ImageResourceConverter" />
        </ResourceDictionary>
    </ContentPage.Resources>

    <StackLayout>

        <Image Source="{Binding ImageResource, Converter={StaticResource ImageResourceConverter}}" />

    </StackLayout>
</ContentPage>

C# Usage

class MyPage : ContentPage
{
  public MyPage()
  {
    Content = new StackLayout
    {
      Children = 
      {
          new Image().Bind(Image.SourceProperty, nameof(ViewModel.ImageResource), converter: new ImageResourceConverter()),
      };
    }
  }
}

[CalvinAllen]

Ah, gotcha. Okay, I’ll pivot to the sample app instead 😃

[brminnick]

My concern is that using Assembly.GetCallingAssembly() could break functionality for folks using multiple csproj files, like so:

solution
│
└───MyMauiApp.csproj
    │   CompanyLogo.png
│   
└───MyLoginPage.csproj

When using Assembly.GetCallingAssembly(),MyLoginPageProject.LoginPage would fail, because ImageResourceConverter would be searching for CompanyLogo.png in the wrong assembly.

You may need to mock-out Application for your tests to get the unit tests working.