.NET Maui XAML Data Binding Failures on Int32 & Doubles

I have a .NET MAUI app using databinding and trying to format values as currency in an Entry field. The property is a double and the binding does work however I get XAML Data Binding Failures. Normal string fields work fine, only when using Double and Int32 do I get these failures. Clearly a double cannot store characters like a dollar sign, comma, or period so the error in general makes sense, but I cannot figure out how to have onscreen formatting but only pass the value without formatting.

public class LeaseAgreement : Base
{
    public string Description { get; set; }
    public DateTime DateLeaseStarted { get; set; }
    public int TotalMonths { get; set; }
    public int AnnualMiles { get; set; }
    public **double ExcessPerMileAmount** { get; set; }

<Label Grid.Row="3" Grid.Column="0" Text="Excess Milage Charge" Style="{StaticResource FormLabel}" />
<Entry Grid.Row="3" Grid.Column="1" Text="{Binding **ExcessPerMileAmount**, StringFormat='{0:C2}'}" Style="{StaticResource FormEntry}" Keyboard="Numeric" />

I've tried databinding with StringFormat (as seen above). I have also tried Behaviors on the Entry field.

The numeric value is captured and the application fully works in Windows, iOS, and Android. However it throws a ton of XAML Data Binding Failures and is messy, especially if using generic exception monitoring.

Any suggestions are greatly appreciated!

Solution

Create a converter that can convert your currency type to a decimal value something similar to this:

public class CurrencyConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return Decimal.Parse(value.ToString()).ToString("C");
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            string valueFromString = Regex.Replace(value.ToString(), @"\D", "");

            if (valueFromString.Length <= 0)
                return 0m;

            long valueLong;
            if (!long.TryParse(valueFromString, out valueLong))
                return 0m;

            if (valueLong <= 0)
                return 0m;

            return valueLong / 100m;
        }
    }

Define the same in your resources an example of this is below:

  <ContentPage.Resources>
    <ResourceDictionary>
      <util:CurrencyConverter x:Key="currencyConverter" />
    </ResourceDictionary>
  </ContentPage.Resources>

Use that in your text property

Text="{Binding SomeProperty, Converter={StaticResource currencyConverter}}"

And the property that you need to bind would be something like this:

    public decimal SomeProperty { get; set; }

If needed you can make this an observable property

This is based on the example I used back in the day for Xamarin forms which can be found here https://gist.github.com/alfeugds/786260ab70a49565070338052ceaee3e