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Multibinding with converter on one of the bindings in .net MAUI

My issue is that when I use a converter on one of the multibinding's binding. It doesn't send the right thing to the converter. As per the DOC(https://learn.microsoft.com/en-us/dotnet/maui/fundamentals/data-binding/multibinding?view=net-maui-7.0) in the Consume a IMultiValueConverter it should work, so I don't know what I'm doing wrong...
My multibinding class is the following:
public class BooleanAndConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values == null || !targetType.IsAssignableFrom(typeof(bool)))
{
return false;
}
foreach (var value in values)
{
if (!(value is bool b))
{
return false;
}
else if (!b)
{
return false;
}
}
return true;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
I have a Boolean inverter class which is the following:
public class InverseBooleanConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (targetType != typeof(bool))
throw new InvalidOperationException("The target must be a boolean");
return !(bool)value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
Then in my XAML I'm using it like so:
<Button Text="Passer à la ronde suivante" Command="{Binding NextRoundCommand}">
<Button.IsVisible>
<MultiBinding Converter="{StaticResource BooleanAndConverter}">
<Binding Path="isGameStarted"/>
<Binding Path="isPlayersPlaying" Converter="{StaticResource InvertedBoolConverter}"/>
</MultiBinding>
</Button.IsVisible>
</Button>
When the inverter converter gets called in the multibinding, instead of receiving a TagetType of bool, it receive a "System.object", so it throws the InvalidOperationException.
Why when using normal bindings it receive a targettype of bool and in multibinding it doesn't?
Thanks

I couldn't see other code, but I tested the sample code DataBindingDemos, it works on my side.
But I found that you didn't implement function ConvertBack for both of your (BooleanAndConverter and InverseBooleanConverter ).
And if I replace the code of ConvertBack to yous as follows, the app will throw exception.
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
You can refer to the following code:
public class InverterConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
bool? b = value as bool?;
if (b == null)
{
return false;
}
return !b.Value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return Convert(value, targetType, parameter, culture);
}
}
public class AllTrueMultiConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values == null || !targetType.IsAssignableFrom(typeof(bool)))
{
return false;
// Alternatively, return BindableProperty.UnsetValue to use the binding FallbackValue
}
foreach (var value in values)
{
if (!(value is bool b))
{
return false;
// Alternatively, return BindableProperty.UnsetValue to use the binding FallbackValue
}
else if (!b)
{
return false;
}
}
return true;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
if (!(value is bool b) || targetTypes.Any(t => !t.IsAssignableFrom(typeof(bool))))
{
// Return null to indicate conversion back is not possible
return null;
}
if (b)
{
return targetTypes.Select(t => (object)true).ToArray();
}
else
{
// Can't convert back from false because of ambiguity
return null;
}
}
}
For more information, you can check: AllTrueMultiConverter.cs and InverterConverter.cs

Binding with IValueConverter does not work

I'm trying to binding the TextColor from a label on ViewCell:
Label myLabel = new Label { Text = "SomeText" };
myLabel.SetBinding(Label.TextColorProperty,
new Binding("TheTextColor", BindingMode.TwoWay, new LabelTextColorConverter()));
Here's the converter:
public class LabelTextColorConverter : IValueConverter
{
public bool OldValue { get; set; }
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
OldValue = (bool) value;
Debug.WriteLine("asdadasdsadsada");
if ((bool)value)
return Color.Red;
else
return Color.Silver;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
Debug.WriteLine("qwqweqewqeeqe");
return OldValue;
}
}
The debug output doesn't appear, and the color doesn't change either. I don't see anything wrong.

Why do you need Two Way binding for this? I don't think it's necessary.
myLabel.SetBinding(Label.TextColorProperty, new Binding("TheTextColor", BindingMode.OneWay, new LabelTextColorConverter()));
Then:
public class LabelTextColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
bool val = (bool)value;
if (val)
return Color.Red;
else
return Color.Silver;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
... and it should work fine. Also make sure you're setting BindingContext for your page/controls correctly.

Multiple culture with textbox

I'm trying to put value (double type) in textbox and i would like to get a custom format.
To explain, i put 10001.1 or 10001,1 and i would like to have 10 001,1 in my texblock.
At the moment my result is 10,001.00 i don't know how can i change the format properly.
My textblock is bind on this :
private double? _Total = null;
public double? Total
{
get
{
if (FiltreAffaire != null)
_Total = ListeAfterFiltre.Sum(CF => CF.CommandeFournisseurLignes.Where(CFL => CFL.Affaire.Numero == FiltreAffaire.Split('-').First().Trim()).Sum(CFL => CFL.Total_HT));
else
return _ListeAfterFiltre.Sum(CF => CF.Montant_HT);
return _Total;
}
set
{
_Total = value;
}
}
Thanks

You can use a simple StringFormat to get your required value... if you are in a country that uses the comma as a decimal separator:
DoubleValue = 10001.1;
...
<TextBlock Text="{Binding DoubleValue, StringFormat={}{0:### ###.#}}" />
In England, this would output the following:
10 001.1
In France, this should output:
10 001,1
You can also do this in code using the NumberFormatInfo class:
NumberFormatInfo numberFormatInfo = new NumberFormatInfo();
numberFormatInfo.NumberDecimalDigits = 1;
numberFormatInfo.NumberDecimalSeparator = ",";
numberFormatInfo.NumberGroupSeparator = " ";
numberFormatInfo.NumberGroupSizes = new int[] { 3 };
string value = DoubleValue.ToString("N", numberFormatInfo);
This outputs:
10 001,1

I finally use something like this (on Textbox) :
CultureInfo ci = (CultureInfo)Thread.CurrentThread.CurrentUICulture.Clone();
ci.NumberFormat.NumberDecimalSeparator = ".";
Thread.CurrentThread.CurrentUICulture = ci;
Thread.CurrentThread.CurrentCulture = ci;
and converter to set value.
ValueConverter="{StaticResource StringToDoubleConverterN3Key}"
public class StringToDoubleConverterN3 : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((double)value).ToString("N3").Replace('.', ',');
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return value;
}
}

Error validation with IDataErrorInfo and IValueConverter

I have a class with a List<string> Tags that I want to display in a TextBox. For this I use a IValueConverter.
ListToStringConverter:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var list = value as List<string>;
var returnvalue = string.Empty;
if(list != null)
list.ForEach(item => returnvalue += item + ", ");
return returnvalue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
var strValue = value as string;
if(strValue != null)
return strValue.Split(new char[] { ',' });
return null;
}
Class Test:
public class Test : IDataErrorInfo
{
public Test()
{
Tags = new List<string>();
}
public List<string> Tags { get; set; }
string errors;
const string errorsText = "Error in Test class.";
public string Error
{
get { return errors; }
}
public string this[string propertyName]
{
get
{
errors = null;
switch (propertyName)
{
case "Tags":
if (Tags.Count <= 1)
{
errors = errorsText;
return "...more tags plz..";
}
break;
}
return null;
}
}
}
Now I want to Validate the Tags:
<TextBox Text="{Binding Test.Tags, Converter={StaticResource ListToStringConverter}, Mode=TwoWay, ValidatesOnDataErrors=True}" />
But there is no error displayed. Maybe because of the conversion but how can i still accomplish a validation?

I don't see why it shouldn't work. If you will run this at first time - SL will highlight the TextBox with red border. But if you will try to change the list of tags - you will see nothing, because you in your converter you have a bug in ConvertBack you return type array of strings (string[]), but property expects object with type List, so you just need to update the ConvertBack method to:
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
var strValue = value as string;
if (strValue != null)
return strValue.Split(new char[] { ',' }).ToList();
return null;
}
One more note about Convert method, you can use Join method:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var list = value as List<string>;
if (list != null)
return String.Join(", ", list);
return null;
}
And one more thing about combining the strings. Don't use operator +, because you can have performance issues with it, use StringBuilder instead.

System.Byte in datagrid column

I am using the following query:
string query = #"SELECT r.id, user_name, user_phone, date_create, REPLACE( date_payment, '0000-00-00 00:00:00', 'Не оплачено' ) as
date_payment, payment_method, amount, rs.name_ru
FROM request AS r, request_status AS rs
WHERE r.status = rs.id";
And i am binding datatemplate in the following way:
DataTemplate>
<TextBlock VerticalAlignment="Center" Text="{Binding date_payment}" Width="135" />
</DataTemplate>
Its throwing correct output except the "date_payment" Its output value comes "System.Byte[]".
please help!!!
Thank from MBen
class ByteArrayToString : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value != null)
{
var listOfBytes = value as Byte[];
string output = "";
output = System.Text.Encoding.UTF8.GetString(listOfBytes);
return output;
}
return "";
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return DependencyProperty.UnsetValue;
}
}

date_payment is an Array, and you didn't provide any way for WPF for displaying it, so it calls ToString . You can provide a data converter for it.
Add a resource to your Window or page :
<Window.Resources>
<local:ByteArrayToString x:Key="ByteArrayConverter" />
</Window.Resources>
Use it in your TextBlock as such :
<TextBlock VerticalAlignment="Center" Text="{Binding date_payement, Converter={StaticResource ByteArrayConverter}}" Width="135" />
Now you need to add a new class that does the conversion :
class ByteArrayToString : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value != null)
{
var listOfBytes = value as Byte[];
string output ="";
output = listOfBytes.Aggregate(output, (current, elemt) => current + elemt.ToString());
return output;
}
return "";
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return DependencyProperty.UnsetValue;
}
}

This thing happened to me to. It seems this is due to a bug in the connector. Try to cast the date column to CHAR. It worked for me.