Xaml - how to use ImageSource from ViewModel

Question

I have an ObservableCollection<Item> and an Item contains both a file path and an ImageSource of some image from the disk.

public ObservableCollection<Item> Items { get; set; } = new ObservableCollection<MediaListItem>();

public class Item
{
    public string Image { get; set; } // Full path to the image
    public ImageSource ImageSource { get; set; }
}

However, I am unable to access any of the two attributes and display an image via XAML.

<ListView ItemsSource="{Binding MediaList}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <StackLayout Padding="10">
                    <Image Source="{Binding ImageSource}" VerticalOptions="Fill"></Image>
                </StackLayout>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

Now I am confused because I am able to output the string Image via XAML through a label, but can't display an image from the path at all.

Answer 1

You can use ImageSource.FromFile() or ImageSource.FromUri() like this

In Xaml

<Image  Source="{Binding  ImageSource}"  Aspect="AspectFit"  ></Image>

In Code

public ObservableCollection<Item> MediaList { get; set; } = new ObservableCollection<Item>()
        {
            new Item
            {
                ImageSource = ImageSource.FromFile("xamarin.png")
            },
            new Item
            {
                ImageSource = ImageSource.FromUri(new Uri("https://i.sstatic.net/4mMod.png"))
            }
        };

The result

Update

Depending on Microsoft-Local Images

Image files can be added to each application project and referenced from Xamarin.Forms shared code...

To use a single image across all apps, the same filename must be used on every platform, and it should be a valid Android resource name (ie. only lowercase letters, numerals, the underscore, and the period are allowed).

For more information take a look at the answer here

Now if you want to display an image without adding it to each platform, you should use Converter.

For example:

1. Create a new folder called ImagesFolder in shared code then add the image to it

   

2. In Code, create a new class called ByteArrayToImageSourceConverter like this

   public class ByteArrayToImageSourceConverter : IValueConverter 
   {
     public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
     {   
       byte[] bytes;
       var assembly = GetType().GetTypeInfo().Assembly; // using System.Reflection;
   
       var stream = assembly.GetManifestResourceStream((string)value); // value = "App1.ImagesFolder.ninja.png"
       using (var ms = new MemoryStream()) // using System.IO; 
       {
           stream.CopyToAsync(ms);
           bytes = ms.ToArray();
       }
       return ImageSource.FromStream(() => new MemoryStream(bytes));
     }
     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
     {
       return null;
     }
   }
   

   View Model

   public ObservableCollection<Item> MediaList { get; set; } = new ObservableCollection<Item>()
   {
       new Item
       {
          Image  = "App1.ImagesFolder.ninja.png"
       }
   };
   

3. In Xaml

   <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
        xmlns:local="clr-namespace:App1"
        x:Class="App1.MainPage">
   
     <ContentPage.Resources>
       <ResourceDictionary>
          <local:ByteArrayToImageSourceConverter  x:Key="ByteArrayToImageSourceConverter" />
      </ResourceDictionary>
    </ContentPage.Resources>
   
    <ListView ItemsSource="{Binding MediaList}" >
       <ListView.ItemTemplate>
         <DataTemplate>
           <ViewCell>
              <Image Source="{Binding Image, Converter={StaticResource ByteArrayToImageSourceConverter}}" />
           </ViewCell>
         </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>
   
   </ContentPage>
   

Related Links

ByteArrayToImageSourceConverter

Shared Resources

How to load binary images in Xamarin?