Define a collection inside XAML

Question

I want to create a Binding to a collection of strings defined inside XAML.

In WPF I could create an ArrayList as a resource with a key, ready to be used as the source of a Binding (using a StaticResource).

Is this possible in Xamarin Forms?

EDIT: I've tried with this XAML with the solution proposed by @Stephane Delcroix, but I'm getting an Unhandled Exception:

<?xml version="1.0" encoding="utf-8"?>

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:sys="clr-namespace:System;assembly=mscorlib"
             x:Class="ReferenceApp.Views.GamesPage"
             Title="Games">


    <ContentPage.Resources>
        <x:Array Type="{x:Type sys:String}" x:Key="array">
            <x:String>Hello</x:String>
            <x:String>World</x:String>
        </x:Array>
    </ContentPage.Resources>
    <Grid />

</ContentPage>

However, the exception is not thrown if I remove the <x:Array >... </x:Array>

What am I doing wrong?

Falange

What control and which property of the control are you trying to bind your list to? I know how to do it for Picker.Items but not sure about a ListView.ItemSource for example. – Zuber

I would like to use the ItemsSource of a ListView – Falange

You might still be able to work off the Picker example here. – Zuber

Answer 1

I see that you are using the XF standard markup extensions. Your mistake seems to be in Type="{x:Type sys:String}", instead of sys:String you should write x:String which appears in the common xmlns:x

In this sample I fill a listview with strings

<ListView Margin="10">
    <ListView.ItemsSource>
        <x:Array Type="{x:Type x:String}">
            <x:String>Hello</x:String>
            <x:String>World</x:String>
        </x:Array>
    </ListView.ItemsSource>            
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <Label Text="{Binding}" />
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>                
</ListView>

Waugh

Answer 2

You can use the built-in x:Array

<x:Array Type="{x:Type sys:String}" x:Key="array">
    <x:String>Hello</x:String>
    <x:String>World</x:String>
</x:Array>

with sys defined as xmlns:sys="clr-namespace:System;assembly=mscorlib"

or any collection you like, e.g. List

<scg:List x:TypeArguments="{x:Type sys:String}" x:Key="genericList">
    <x:String>Hello</x:String>
    <x:String>World</x:String>
</scg:List>

with sys defined as before, and scg being xmlns:scg="clr-namespace:System.Collections.Generic;assembly=mscorlib"

Locarno

I've tried it, but in Android I'm getting an Unhandled Exception. Please, see my edit in the OP. – Falange

String is not defined in System.Runtime but in mscorlib if I'm not mistaken – Locarno

Also, modifying questions usually makes the answer irrelevant, so please avoid doing that. – Locarno

Sorry, but I don't know any other way to paste the XAML. – Falange

BTW, I've modified the XAML with the xmlns poiting to mscorlib and it happens the same: I get an Unhandled Exception. – Falange

this snippet was copy pasted from my unit tests of the XF xaml parser, so it should work. if it does not, please report a bug – Locarno

Answer 3

This is an answer to the updated question.

<x:string> only supports constant values. You can address this issue with a Markup Extension

Its functionality is trivial: it returns its parameter.

using System;
using Xamarin.Forms.Xaml;

namespace YOURAPP.Extensions
{
    public class StringExtension : IMarkupExtension
    {
        public string Value { get; set; }

        public object ProvideValue(IServiceProvider serviceProvider)
        {
            return Value;
        }
    }
}

Use it like this in a view:

1. Add xmlns:ext="clr-namespace:YOURAPP.Extensions" to the root element
2. <ext:StringExtension Value="{anything here}" /> where you would otherwise want <x:string>

Note that this causes an Add to be called to the IEnumerable. For custom controls you would need initialization (to avoid a NullReferenceException) and and ObservableCollection to make sure that the view is updated on adding.

Acrobatic