Develop Reference

ObjectlistView Checkbox Issue

I have an issue trying to get a Checkbox working with ObjectListview.
My model looks like this:
public class object
{
public string name {get; set;}
public int age {get; set;}
public bool inuse {get; set;}
}
And I added a FastObjectListView via the Designer in Visual Studio to a Win Forms Application.
Then, I added the Columns and set the AspectName for each column to the Models Property (First column: AspectName: name, Second Column: AspectName: age, Third Column: AspectName: inuse).
Afterwards, I filled the ListView with this:
using (var context = new objectDb())
{
var objectlist = context.objects.ToList();
fastoLV_Clean.SetObjects(objectlist);
fastoLV_Clean.Refresh();
}
That works, and I can see my Database entries in the ListView.
Now I want to add a CheckBox column where someone can check or uncheck the items to delete them and I can not get the checkbox to work.
I have added a Column and set CheckBox to true, changed the CheckedAspectName of the ListView and now I can see the Checkboxes but nothing happens if I click them to check.
I think I'm on the completely wrong track, what do I have to do to make it work?
Thank you very much!!

I don't know a way with the ObjectListView to include any items which are not part of your model.
So then the simple way is to change your model to include a "Delete" property which you can then show in your ObjectListView.
Of course, this is not always possible! Especially if you are dealing with items that are written to/from Database or another persistence layer.
Then the trick is to write a derived class with you model being the base class and then you just add the delete column to this. But then you would need to convert from your Base to a derived class before showing in the ObjectListView.
The following code can help with that.
You keep your columns set-up as you have already done.
Assuming your (now base) class is defined like this
public class MyClass
{
public string name { get; set; }
public int age { get; set; }
public bool inuse { get; set; }
}
Your derived class inherits from this, adds the delete property and a new constructor
public class MySecondClass : MyClass
{
public bool Delete { get; set; }
public MySecondClass(MyClass other)
{
//Copy from MyClass
this.name = other.name;
this.age = other.age;
this.inuse = other.inuse;
//Set default for new properties
this.Delete = false;
}
}
Your code to retrieve the objects and set them then looks like this
using (var context = new objectDb())
{
var objectlist = context.objects.ToList();
//Now we need to convert to the derived class type
var secondlist = list.ConvertAll(x => new MySecondClass(x));
//Then we setobjects using this new list
fastoLV_Clean.SetObjects(secondlist);
}

How to set listview itemssource to a viewmodel in Xamarin?

I'm trying to make a listview in xamarin show data from a restapi but have the option to filter the list or sort it based upon last name.
I've set the bindingcontext equal to the apiviewmodel which works. But I want to set the itemssource to a list which can be manipulated later instead of the binding context.
Here is the code that works:
Xaml:
<ListView x:Name="DirectoryListView" ItemsSource="{Binding ContactsList}" IsPullToRefreshEnabled="True">
Xaml.cs:
LocalAPIViewModel = new APIViewModel();
BindingContext = LocalAPIViewModel;
APIViewModel.cs:
private List<MainContacts> _ContactsList { get; set; }
public List<MainContacts> ContactsList
{
get
{
return _ContactsList;
}
set
{
if(value != _ContactsList)
{
_ContactsList = value;
NotifyPropertyChanged();
}
}
}
public class MainContacts
{
public int ID { get; set; }
public string FirstName { get; set; }
}
This all works fine. It's only when I add the following lines that it stops displaying the data in the listview:
xaml.cs:
LocalList = LocalAPIViewModel.ContactsList;
DirectoryListView.ItemsSource = LocalList;
I think I need to add these lines so that I can manipulate the list that's being displayed. Why is the list not being displayed? Is this not how it should be done?

According to your description and code, you use MVVM to bind ListView firstly, it works fine, now you want to use Viewmodel to bind ListView itemsource in xaml.cs directly, am I right?
If yes,I do one sample according to your code, that you can take a look, the data can display successfully.
public partial class Page4 : ContentPage
{
public APIViewModel LocalAPIViewModel { get; set; }
public Page4 ()
{
InitializeComponent ();
LocalAPIViewModel = new APIViewModel();
listview1.ItemsSource = LocalAPIViewModel.ContactsList;
}
}
public class APIViewModel
{
public ObservableCollection<MainContacts> ContactsList { get; set; }
public APIViewModel()
{
loadddata();
}
public void loadddata()
{
ContactsList = new ObservableCollection<MainContacts>();
for(int i=0;i<20;i++)
{
MainContacts p = new MainContacts();
p.ID = i;
p.FirstName = "cherry"+i;
ContactsList.Add(p);
}
}
}
public class MainContacts
{
public int ID { get; set; }
public string FirstName { get; set; }
}
so I suggest you can check ContactsList if has data.
Update:
I want to be able to search the list with a search bar and also order it by first or last names. I also want to be able to click on one of the contacts and open up a separate page about that contact
I do one sample that can meet your requirement, you can take a look:
https://github.com/851265601/xf-listview

So, to answer all your questions...
First, the binding.
Once you set the ItemsSource="{Binding ContactsList}" this means that anytime you signal that you have changed your ContactsList by calling OnPropertyChanged(), that is going to be reflected on the ItemsSource property (so, update the UI - that is why we put the OnPropertyChanged() into the setter). Thus, you do not need to manually set the ItemsSource every time you change it. (Especially from the View, as the View should have no knowledge of how the ContactsList is defined in the ViewModel.)
So you can completely remove those lines from the View's code-behind.
Next, the ordering and searching.
What OnPropertyChanged() does, is that it re-requests the bound property from the ViewModel, and updates the View according to that. So, just after OnPropertyChanged() is called, the getter of the bound property (ContactsList) is called by the View.
So, a good idea is to put the sorting mechanism into the getter of the public property. (Or the setter, when resetting the property.) Something like this:
public class ViewModel {
private ObserveableCollection<MainContacts> contactList { get; set; }
public ObserveableCollection<MainContacts> ContactList {
get {
return new ObservableCollection<MainContacts>(contactList
.Where(yourFilteringFunc)
.OrderBy(yourOrderingFunc));
}
set {
contactsList = value;
OnPropertyChanged();
}
}
//...
}
So, whenever your public property is called, it will sort the private property and return the collection that way.

Change public List<MainContacts> ContactsList to public ObservableCollection<MainContacts> ContactsList
in xaml.cs
instead of LocalList = LocalAPIViewModel.ContactsList;, put
ContactsList = new ObservableCollection(LocalAPIViewModel.ContactsList);
I think this will work, instead of setting ListView's Itemsource to 'LocalList'

Add Tag to ComboBox Items From Model

I have a TypeOfContact model that is made up of an ID, and Text. For example, one type would be Telephone and the ID would be 1. Another type would be Email and the ID 2.
What I would like to do is add the text of the TypeOfContact as an item and the ID as a tag. I imagine it would look something like this, however this isn't working;
contactTypeComboBox.Items.Clear();
foreach (TypeOfContact c in ContactTypes)
{
contactTypeComboBox.Items.Add(c.ContactTypeText);
foreach (ComboBoxItem item in contactTypeComboBox.Items)
{
item.Tag = c.ContactTypeID;
}
}
The reason I want to do this is that when someone selects one of the ComboBox items I want to store the text and the ID. I could do this all through XAML but ContactTypes is a list that is populated by the user, so I cannot hard code the values into the ComboBox as maintaining it and adding new TypesOfContact would be difficult.

I fixed this issue myself by first adding;
DisplayMemberPath="ContactTypeText" SelectedValuePath="ContactTypeID"
to the XAML of the ComboBox then accessing the ID like;
contactTypeComboBox.SelectedValue

In your situation i would bind the list of your TypeOfContacts as ItemsSource to the ComboBox. After that you could set the tag, but i think you don't will need it, because when you also bind the SelectedItem you got back the whole item (ID, type, ...) and can work with it in other parts of your code.
Example for simplifying without a ViewModel (but you should use one):
Codebehind
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = this;
FillListWithSomeExamples();
}
private void FillListWithSomeExamples()
{
TypesOfContacts.Add(new TypesOfContact {Id = 1, Type = "Email"});
TypesOfContacts.Add(new TypesOfContact { Id = 2, Type = "Telephone" });
}
public TypesOfContact SelectedTypesOfContact { get; set; }
public ObservableCollection<TypesOfContact> TypesOfContacts { get; set; } = new ObservableCollection<TypesOfContact>();
}
TheTestmodel:
public class TypesOfContact
{
public int Id { get; set; }
public string Type { get; set; }
}
XAML
<Grid>
<ComboBox ItemsSource="{Binding TypesOfContacts}" SelectedItem="{Binding SelectedTypesOfContact}" DisplayMemberPath="Type"/>
</Grid>
Now you can read the selected item in any other method of the MainWindow by looking at SelectedTypesOfContact.

Interacting with bound DTO using MVVM

I'm currently Binding my Listbox to a DTO. Following MVVM patterns, How do I interact with what was selected from the Listbox.
I want something like this [1 being the "FileName"
If (Listbox.Selecteditem[1] == "samplefilename")
{ Messagebox.Show("Files matched"}
But how exactly is that done using MVVM? Do I have to create SelectedValue bindings/properties?
public class FilesDTO : IDTO
{
public int Id { get; set; }
public string FileName { get; set; }
public string FileExtension { get; set; }
public byte[] FileArray { get; set; }
}

You just need to add a "SelectedFileDTO" to your ViewModel and in your XAML, make sure it's set to TwoWay. When it changes in the View, your SelectedFileDTO setter will be hit in your ViewModel.
<ListBox ItemsSource={Binding Files} SelectedItem={Binding SelectedFileDTO, Mode=TwoWay}/>
public FilesDTO SelectedFileDTO
{
get...
set...
}

Yes, you should bind the SelectedValue property to a DependencyProperty. Then whenever you want to use it, it is right there at your disposal. You could also give the DependencyProperty changed events to utilize.

Sorting ObservableCollection Using Custom Logic

New to WPF and also the ObservableCollection I need to sort it in my own way, and keep it sorted everytime something adds or removes from it.
ObservableCollection<User> users = new ObservableCollection<User>();
The user object is like so :
class User
{
public string Name { get; set; }
public bool IsOp { get; set; }
public bool IsAway { get; set; }
}
I would like all the IsOp's at the top of the list, in alphabetical order. Then all the non-ops in alphabetical order following them.
What is the correct way to achieve this?
Many thanks in advance.

The easiest way is to use a CollectionView:
ICollectionView view = CollectionViewSource.GetDefaultView(users);
view.SortDescriptions.Add(new SortDescription("IsOp", ListSortDirection.Descending));
view.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
When you will bind the view to that list, the items will appear in the specified order.
Using the trick shown here, you can even use Linq:
var query =
from u in users.ShapeView()
orderby u.IsOp descending, u.Name ascending
select u;
query.Apply();