Binding: Property not found

Question

Hi,

Complete beginner here!
I am trying to create a simple ListView using Mvvmhelpers and I am having trouble with data binding.

.xaml

<?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:model="clr-namespace:Test.Models"
             xmlns:viewmodels="clr-namespace:Test.ViewModels"

             x:Class="Test.Views.DataContainerPage"
             x:DataType="viewmodels:DataContainerViewModel">

    <ContentPage.BindingContext>
        <viewmodels:DataContainerViewModel/>
    </ContentPage.BindingContext>

    <ListView CachingStrategy="RecycleElement"
              ItemsSource="{Binding DataContainers}">

        <ListView.ItemTemplate>
            <DataTemplate x:DataType="model:DataContainer">
                <ViewCell>
                    <Grid>
                        <Label Text="{Binding ID}"/>
                    </Grid>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>

    </ListView>
</ContentPage>

xaml.cs

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace Test.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class DataContainerPage : ContentPage
    {
        public DataContainerPage()
        {
            InitializeComponent();
        }
    }
}

Class I want to use in my DataTemplate

        namespace Test.Models
        {
            public class DataContainer
            {
                public string ID;
            }
        }

And finally my viewmodel class:

using MvvmHelpers;
    using Test.Models;

    namespace Test.ViewModels
    {
        public class DataContainerViewModel : BaseViewModel
        {
            public ObservableRangeCollection<DataContainer> DataContainers { get; set; }

            public DataContainerViewModel()
            {
                DataContainers = new ObservableRangeCollection<DataContainer>();

                DataContainers.Add(new DataContainer { ID = "0" });
                DataContainers.Add(new DataContainer { ID = "1" });
                DataContainers.Add(new DataContainer { ID = "2" });
            }
        }
    }

If I try to bind the label text to the DataContainer.ID visual studio auto-completes ID for me, so something is working here.
But if I try to run the app I get the builderror:
Binding: Property "ID" not found on "Test.Models.DataContainer".
Do you guys have any idea why this is failing in this case? I have code where this kind of binding works .. in the same project.

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

I made a demo according to your code, it works properly. The code is as follows,

1.class DataContainer

public class DataContainer  
{  
    public string ID { get; set; }  
}  

2.class DataContainerViewModel

 public class DataContainerViewModel  
{  
    public ObservableCollection<DataContainer> DataContainers { get; set; }  

    public DataContainerViewModel()  
    {  
        DataContainers = new ObservableCollection<DataContainer>();  

        DataContainers.Add(new DataContainer { ID = "0" });  
        DataContainers.Add(new DataContainer { ID = "1" });  
        DataContainers.Add(new DataContainer { ID = "2" });  
    }  
}  

3.MainPage.xaml

  <?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:formapp1="clr-namespace:FormApp1"  
             x:Class="FormApp1.MainPage">  


    <ContentPage.BindingContext>  
        <formapp1:DataContainerViewModel></formapp1:DataContainerViewModel>  
    </ContentPage.BindingContext>  

    <StackLayout>  
        <ListView CachingStrategy="RecycleElement"  
               ItemsSource="{Binding DataContainers}">  
            <ListView.ItemTemplate>  
                <DataTemplate >  
                    <ViewCell>  
                        <Grid>  
                             <Label Text="{Binding ID} " TextColor="Red" HorizontalOptions="Center" FontSize="Large"/>  
                        </Grid>  
                    </ViewCell>  
                </DataTemplate>  
            </ListView.ItemTemplate>  
        </ListView>  
    </StackLayout>  
</ContentPage>  

Note:

1. For ID in class DataContainer, add { get; set; } ;

2.We don't need add x:DataType in xaml file for our page;(You can check above code);
3.To make the UI look better, I use the following code :

<Label Text="{Binding ID} " TextColor="Red" HorizontalOptions="Center" FontSize="Large"/>  

The result is:

For more details, you can refer the official document : https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/listview/

Best Regards,

Jessie Zhang

---

If the response is helpful, please click "Accept Answer" and upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.