Xamarin Converter not working on IsEnabled Property

Question

I am using a converter code below

namespace someAssembly.Converters
{
    public class ValidateTextLengthConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return (int)value != 0;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return (bool)value ? 1 : 0;
        }
    }
}

Here is my Xaml

Namespace:

xmlns:converter="clr-namespace:someNamepsace.someAssembly.Converters;assembly=someAssembly"

Resources:

  <ContentPage.Resources>
     <ResourceDictionary>
         <converter:ValidateTextLengthConverter x:Key="validateLength" />
    </ResourceDictionary>
  </ContentPage.Resources>

Usage: (edit I added the textbox being refered by converter)

<StackLayout HorizontalOptions="FillAndExpand">
<Label Text="Name:" />
<Entry x:Name="txtName" Text="{Binding Name}" HorizontalOptions="FillAndExpand" />
</StackLayout>

<Button x:Name="btnSave" Text="Save" 
Command="{Binding SaveCommand}"
HorizontalOptions="EndAndExpand" 
BackgroundColor="{x:Static local:ColorResources.ButtonColorTransparent}" 
IsEnabled="{Binding Source={x:Reference txtName},
Path=Text.Length,
Converter={StaticResource validateLength}}"  />

My main purpose is to disable a button when a textbox length is still zero. It seems that Converter or IsEnabled is not firing. Is there something wrong with my code?

Answer 1

Oh well, There's nothing wrong with the code. The error is in my Bindable property where the value needs to be initialized.

From:

private string _Name; //<-- not initialized, Null
public string Name
{
    get { return _Name; }
    set { SetProperty(ref _Name, value); }
}

To:

private string _Name = string.Empty; //<-- needs to be empty or "" string
public string Name
{
    get { return _Name; }
    set { SetProperty(ref _Name, value); }
}

But inspite of a working converter, I opted to use a DelegateCommand so I can check for the length of more than one properties.

public DelegateCommand SaveCommand { get; private set; }

SaveCommand = new DelegateCommand(SaveItem, canExecute)
        .ObservesProperty(() => this.Name)
        .ObservesProperty(() => this.Title)
        .ObservesProperty(() => this.Description);




public bool canExecute()
{
    return !string.IsNullOrEmpty(this.Name) &&    !string.IsNullOrEmpty(this.Title) && !string.IsNullOrEmpty(this.Description);
}


private async void SaveItem()
    {
       //Put your saving logic here.
    }

Answer 2

I think you should bind to Text property which is bindable, instead of its length. Then you should modify the converter to handle string instead of int.