Xamarin Forms Currency Mask for Entry fields

CurrencyConverter.cs

using System;
using System.Globalization;
using System.Text.RegularExpressions;
using Xamarin.Forms;

namespace MyProject.Util
{
    /// <summary>
    /// Converter for using in Entry fields for masked input of currency.
    /// <para>The binded property must be of type decimal, and must invoke the PropertyChangedEventArgs event whenever the value is changed, so that the desired mask behavior is kept.</para>
    /// </summary>
    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;
        }
    }
}

SomeView.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:util="clr-namespace:MyProject.Util;assembly=MyProject"
             x:Class="MyProject.View.SomeView"
             Title="Some View">
  <ContentPage.Resources>
    <ResourceDictionary>
      <util:CurrencyConverter x:Key="currencyConverter" />
    </ResourceDictionary>
  </ContentPage.Resources>
  <ContentPage.Content>
    <StackLayout Padding="20">
      <Entry x:Name="ValueConvert" Placeholder="Value" Text="{Binding SomeProperty, Converter={StaticResource currencyConverter}}" Keyboard="Numeric" />
      <!-- your fields go here -->
    </StackLayout>
  </ContentPage.Content>
</ContentPage>

SomeViewModel.cs

//Create a property in the ViewModel that wraps the decimal property/model you want to receive the currency value
public decimal SomeProperty
{
    get {
        return YourDecimalProperty; 
    }
    set
    {
        YourDecimalProperty = value;

        //invoke PropertyChangedEventArgs here
        //...
    }
}

Good work!!!

very nicely done!

Works great!

Work like a charm!
I've also managed to specify a culture in case anyone needs:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            NumberFormatInfo nfi = new CultureInfo("pt-BR").NumberFormat;
            return Decimal.Parse(value.ToString()).ToString("C", nfi);
        }

Personally, does it work on xamarin.forms 2.3.4.270?
Mine is not returning the mask

How do I invoke PropertyChangedEventArgs, can you help me with that?

Just that..

private decimal _decimalConverter;
    public decimal DecimalConverter
        {
            get => _decimalConverter;
            set
            {
                _decimalConverter = value;
                OnPropertyChanged(nameof(DecimalConverter));
            }
        }

And then
Text="{Binding DeciamConverter, StringFormat='{0:N0}'}"

how allow negative numbers?

You'd probably need to change the ConvertBack() method logic to preserve the negative sign entered from the input.
I'd change the Regex.Replace call to some conditional logic, see if there's a negative sign before any number, and then return the negative number.
It's been a while since I don't play with C# so I can't test it right now =/

I must be doing something wrong..
I always see in the entry text Gs. 0

I have a problem about formatting. I tryed all of sample project . When I want to delete amount , comma is not skipped. For Example , entry amount default : 0,00
I entry 12.345,34 . I pressed backspace key for once. Amount: 1.234,53 , Normally I would expect to set as 12.345,30.

Also When I started to write amount, 0,00 amount isn't deleted. For Example I want to write "3". Amount set as 30,00 .

I can't find where I'm doing wrong. Could you help me with that please ?

great work, thank you so much for this.

how allow negative numbers?

public class DecimcalCurrencyConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return decimal.Parse(value.ToString()).ToString("$0.00;-$0.00");
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var isNegative = Regex.IsMatch(value.ToString(), "^-", RegexOptions.CultureInvariant);
        string valueFromString = Regex.Replace(value.ToString(), @"\$|,", "");
        if (valueFromString.Length <= 0)
        {
            return 0m;
        }

        if (!decimal.TryParse(valueFromString, out var decimalVal ))
        {
            return 0m;
        }

        return isNegative ? decimalVal * -1 : decimalVal ;
    }
}

I have the same problem :
I have a problem about formatting. I tryed all of sample project . When I want to delete amount , comma is not skipped. For Example , entry amount default : 0,00
I entry 12.345,34 . I pressed backspace key for once. Amount: 1.234,53 , Normally I would expect to set as 12.345,30.

Also When I started to write amount, 0,00 amount isn't deleted. For Example I want to write "3". Amount set as 30,00 .

I can't find where I'm doing wrong. Could you help me with that please ?