C#•3y ago

❔ WPF data binding

Hello, I'm new into wpf developing. I'm trying to bind textbox's data to a property, but it seems to work only for getter, not setter. when I manually set the property and run the app, the textbox is filled by the property. But when, in the app, I change textbox's data, it doesn't update the property. Can somebody help me ?

HimmDawg•6/13/23, 9:46 AM

Can you show us, how you set up the binding?

PetitKinderOP•6/13/23, 9:48 AM

I will try to do so

PetitKinderOP•6/13/23, 9:48 AM

PetitKinderOP•6/13/23, 9:48 AM

here a textbox's Text is binded to a Scene property

PetitKinderOP•6/13/23, 9:49 AM

PetitKinderOP•6/13/23, 9:49 AM

here is the property

PetitKinderOP•6/13/23, 9:50 AM

PetitKinderOP•6/13/23, 9:51 AM

here is my view

PetitKinderOP•6/13/23, 9:53 AM

PetitKinderOP•6/13/23, 9:53 AM

and that's the viewModel

PetitKinderOP•6/13/23, 9:53 AM

sorry that's a bit messy

HimmDawg•6/13/23, 10:05 AM

And where are you setting the DataContext?

HimmDawg•6/13/23, 10:07 AM

Furthermore, your second Textbox in

ShotTheme.xaml

ShotTheme.xaml

binds to

shot

shot

which does not exist. You'll have to use

Shot

Shot

.
And your Shot property will need to notify the UI when something changed as well

HimmDawg•6/13/23, 10:10 AM

Instead of

public string Scene
{
  get 
  {
    return _scene;
  }
  set
  {
    _scene = value;
    OnPropertyChanged();
  }
}

public string Scene
{
  get 
  {
    return _scene;
  }
  set
  {
    _scene = value;
    OnPropertyChanged();
  }
}

You can use

public string Scene
{
  get => _scene;
  set => SetProperty(ref _scene, value);
}

public string Scene
{
  get => _scene;
  set => SetProperty(ref _scene, value);
}

Or even drop the entire property
and do just this

[ObservableProperty]
private string _scene;

[ObservableProperty]
private string _scene;

The last example creates some source-generated files, so you'll still be able to use

Scene

Scene

in your code and XAML, even though you never specifically declared it.

This makes it more readable :)

HimmDawg•6/13/23, 10:11 AM

So for

Shot

Shot

you'll have to choose one of those 3 ways to notify your UI

HimmDawg•6/13/23, 10:12 AM

The same applies for

Environment

Environment

HimmDawg•6/13/23, 10:17 AM

So I checked the docs. So most of the time, bindings have a default value for

UpdateSourceTrigger

UpdateSourceTrigger

PropertyChanged

PropertyChanged

. However this doesn't apply to textboxes. So you'll 1.) have to set the binding mode of your bindings to

TwoWay

TwoWay

and then, you'll have to set the

UpdateSourceTrigger

UpdateSourceTrigger

of your binding to

PropertyChanged

PropertyChanged

HHimmDawg And where are you setting the DataContext?

PetitKinderOP•6/13/23, 10:25 AM

which one ? In the view I'm setting the datacontext for the ShotListViewModel, but I don't know if this is the one you talking about

HHimmDawg Furthermore, your second Textbox in `ShotTheme.xaml` binds to `shot` which does ...

PetitKinderOP•6/13/23, 10:27 AM

isn't it what the OnpropertyChanged element is for ?

HHimmDawg Instead of ```cs public string Scene { get { return _scene; } set ...

PetitKinderOP•6/13/23, 10:31 AM

for this last exemple, do I need to generate the ObservableProperty class ?

PPetitKinder which one ? In the view I'm setting the datacontext for the ShotListViewModel, b...

HimmDawg•6/13/23, 10:36 AM

No, I meant the ShotTheme. Are you setting the datacontext there?

PPetitKinder isn't it what the OnpropertyChanged element is for ?

HimmDawg•6/13/23, 10:37 AM

Yes, but only for Shot. All other properties wont notify the UI because they dont have this in your VM

PPetitKinder for this last exemple, do I need to generate the ObservableProperty class ?

HimmDawg•6/13/23, 10:38 AM

No, it's part of the CommunityToolkit

you can use it in every class that derives from ObservableObject

HimmDawg•6/13/23, 10:48 AM

ah wait.. i noticed that theres no CommunityToolkit in your usings. ObservableObject is your own implementation then? In that case you'll have to go with the first way ^^

PetitKinderOP•6/13/23, 10:48 AM

Using the lambda sign ?

HHimmDawg No, I meant the ShotTheme. Are you setting the datacontext there?

PetitKinderOP•6/13/23, 10:50 AM

I need to set dataContext for a theme ?

PPetitKinder I need to set dataContext for a theme ?

PetitKinderOP•6/13/23, 10:50 AM

Because I'm declaring a resourceDictionary for it in the app.xaml

PPetitKinder Using the lambda sign ?

HimmDawg•6/13/23, 10:52 AM

Nah, just go the same way as with your

Scene

Scene

property

HimmDawg•6/13/23, 10:53 AM

I falsely assumed that

ObservableObject

ObservableObject

comes from a package that is widely used in WPF. That package also has a class called

ObservableObject

ObservableObject

and it provides the same functionality. They just added a few extras

PPetitKinder I need to set dataContext for a theme ?

HimmDawg•6/13/23, 10:54 AM

If you want to bind stuff to the controls in it, then you'll have to have some sort of DataContext

PetitKinderOP•6/13/23, 12:03 PM

How do I do so ?

PetitKinderOP•6/13/23, 12:04 PM

What I don't understand, is that the binding works half way

HimmDawg•6/13/23, 1:17 PM

That's because

Furthermore, your second Textbox in ShotTheme.xaml binds to shot which does not exist. You'll have to use Shot.

HimmDawg•6/13/23, 1:17 PM

Binding to Properties is case-sensitive

PetitKinderOP•6/13/23, 2:03 PM

Yeah I know, I was working first on Scene. But scene doesn't work neither

HimmDawg•6/13/23, 2:07 PM

Side-question. Do you really have to bind data into a theme?

PetitKinderOP•6/13/23, 2:12 PM

Well the listView is composed of items defined in the ShotTheme

PetitKinderOP•6/13/23, 2:13 PM

But I suppose it's possible to bind into a theme

PetitKinderOP•6/13/23, 2:17 PM

When the element scene of the object is set in the code, it's working because the textbox is set with the value defined. So the binding is working. But when in the app I modify the property, if I print scene in the output window, the value isn't updated.

HimmDawg•6/13/23, 2:49 PM

No, I meant: Do you specifically have to bind stuff in your theme?

HimmDawg•6/13/23, 2:50 PM

You'd still need a DataContext to bind data. A resource dictionary can't have a datacontext

PetitKinderOP•6/13/23, 2:57 PM

I need to bind the text of textbox which are in the theme, so idk how I can do without it.

HimmDawg•6/13/23, 3:11 PM

Try to replace the controltemplate with a datatemplate and specify the datatype

PetitKinderOP•6/13/23, 8:14 PM

yeah it seems to be a problem around the template, but I'm not used to xaml enough to re-template everything, I think I will have to do some research

HimmDawg•6/13/23, 10:04 PM

So tl;dr
If you just replace "ControlTemplate" with "DataTemplate", you can then assign a

DataType

DataType

to the template. If you do that, you can then use the properties of this datatype in Bindings of control properties within the template

PetitKinderOP•6/13/23, 10:08 PM

But can I do that within a style ?

PetitKinderOP•6/13/23, 10:09 PM

because my listView has the property ItemContentStyle set to the style ShotTheme

PetitKinderOP•6/13/23, 10:09 PM

so I need a style, but if I'm right I can't use dataTemplate in a style

PetitKinderOP•6/13/23, 10:14 PM

I will try using a dataTrigger outside Style

PetitKinderOP•6/13/23, 10:22 PM

well no I can't do that