CODEWITHSUNDEEP
c#xamarinxamarin.formspicker
Hikari
Hikari

Reputation: 599

Xamarin binding count of ItemSource

I need to enable/disable using XAML, a Picker based on the number of elements in it ItemsSource.

<Picker 
    ItemsSource="{Binding WoSpesaDett.DsTecnico}" 
    ItemDisplayBinding="{Binding Valore}" 
    SelectedItem="{Binding WoSpesaDett.Tecnico}" 
    IsEnabled="{Binding ???}" 
    Grid.Row="0" Grid.Column="3"/>

I have tried to use WoSpesaDett.DsTecnico.Count > 0 but it not works.

How can I achieve this?

Thank you!

Upvotes: 0

Views: 1340

Answers (3)

EvZ
EvZ

Reputation: 12169

Note:

If you need to change the visibility of your Picker only once (not in dynamic manner), then create a converter like other answers pointing out.

Otherwise:

In theory dynamically hiding or showing a UI control is very simple. All you have to do is to introduce a boolean property in your model that should look like this for example:

public bool MyPickerShouldBeVisible => WoSpesaDett.DsTecnico.Count > 0;

Now the problem is that you need to notify your View about changes related to MyPickerShouldBeVisible. I am usually using Fody.PropertyChanged to handle the INotifyPropertyChange stuff. Using it you could mark your DsTecnico property with a special attribute AlsoNotifyFor(nameof(MyPickerShouldBeVisible)) to make this solution work.

Here is a full example, ViewModel data is simplified:

// INotifyPropertyChanged should be handled by `Fody.PropertyChanged`
public class MyViewModel : INotifyPropertyChanged
{
  public IList<string> MyData { get; set; }
  [AlsoNotifyFor(nameof(MyPickerShouldBeVisible))]
  public bool ShouldShowPicker => MyData.Any();
}

Using the example above, will result in a dynamic behaviour of you picker.

Upvotes: 1

SushiHangover
SushiHangover

Reputation: 74124

IValueConverter for integer to bool:

public class IntToBooleanConverter : IValueConverter
{
    public object Convert (object value, Type targetType, object parameter, CultureInfo culture)
    {
        int minimumLength = System.Convert.ToInt32 (parameter);
        return (int)value >= minimumLength;
    }

    public object ConvertBack (object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException ();
    }
}

Upvotes: 1

Csharpest
Csharpest

Reputation: 1268

You can either create a bool in your binding context:

public bool PickerShouldBeEnabled
{
    get { return WoSpesaDett.DsTecnico.Count > 0; } //returns true if there are more than 0 elements
}

or for better performance use linq "Any()", if u just wanna enable it if there are any elements in the list

public bool PickerShouldBeEnabled
{
    get { return WoSpesaDett.DsTecnico.Any(); } //returns true if there are any elements
}

Or you can create an IValueConverter that takes the list as the value and returns true based on the count of the list elements. I could give you a basic converter for this situation as well.

Upvotes: 0

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