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Hi Everyone ! i have this project in which i need to Retrieve a list of data, when i click the Retrieve Button, the app enters in break mode and shows me an error saying
System.InvalidCastException: 'Specified cast is not valid.'
Accroding to what i've found the issue is with the ListView block, but im not quite sure, please find it here attached
<ListView x:Name="ListEstudiantes">
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Name}">
</TextCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
If you need a Demo please let me know!
Where do you set set the ItemSource?
You must have an ObservableCollection and set ItemSource property to the collection, otherwise your listview does not know data to visualize
Hi @Alessandro Caliaro What do you mean with Observable collection? can you explain i little more on this ? as i said, im super new on this and so far i've been following the Microsoft Documentation and that tutorial i just provided, and i didn't saw anything like that on those links :/ can you provide some steps or maybe if i provide you this [demo][1] you can maybe explain it with a practical example or something ?
Regards
TestBindingWithListView
you can find the ObserveblaCollection inside the MyPageViewModel.cs
public ObservableCollection<Model> List { get; set; } = new ObservableCollection<Model>();
and the method private void addRows() fills the List
I use csharp to create the page, not xaml, but it's the same...
I set the ItemSource with
lv.SetBinding(ListView.ItemsSourceProperty, "List");
Hi @Alessandro Caliaro I see what you mean, i updated the program and the List View is now working properly according to the specified function, the things is that i need to Search an Student by an specific condition and display the information in the Text Fields, but when i do it the exception pops up, but the List View is working now properly, so im not quite sure how to fix it can you take a look at the Demo please ?
Regards
I suggest to close this thread , upvote my answer and open a new answer with the new problem
It's simple.
ListView need an ItemSource. I don't see that you set an ItemSource in your xaml.
Set it!
For example, here the ItemSource is set in the codebehind: Custom
but you can also use it as a normal xml binding.
Hello,
Welcome to our Microsoft Q&A platform!
the things is that i need to Search an Student by an specific condition and display the information in the Text Fields, but when i do it the exception pops up, but the List >View is working now properly
Do you meen when you click the btnRetrive, when you will get the Specified cast is not valid. Xamarin.Forms?
If so, you should change txtCedula to txtCedula.Text like following code. Because txtCedula is entry, if you want to get the text from the entry, you could add Text property.
var Estudiante = await FireBaseHelper.GetEstudiante(Convert.ToInt32(txtCedula.Text)).ConfigureAwait(true);
Note: If you solved this issue, please delete the demo link in the comment, it contains your privacy information, If you have any other issues about firebase, you do not share the baseUrl. Just emty it, then share test record's data-structor in firebase DB.
Best Regards,
Leon Lu
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Hi @Alessandro Caliaro im using
ItemTemplateonly, it is really necessary to useItemSource? ive read the documentation about ListViews Here still doesnt says that we gotta use the ItemSource as a mandatory thing, also im following this tutorial over Here in order to create this app, since im really new at this.Hope you can help me.
Regards