Hi,
I understand this library is called CalBinding and so this may be out of scope but
it would be nice if bindings could parse complex c# expression so it could substitute some trivial converter class. Example:

public class OverlayVisibleConverter : BaseConverter, IMultiValueConverter
{
    public object Convert( object[] values, Type targetType, object parameter, CultureInfo culture )
    {
        bool isKeyboardFocusWithin = (bool)values[ 0 ];
        var passwordBox = (PasswordBox)values[2];

        bool visibile = !isKeyboardFocusWithin && String.IsNullOrEmpty( passwordBox.Password );
        return visibile ? Visibility.Visible : Visibility.Collapsed;
    }  
}


<Label.Visibility>
        <MultiBinding Converter="{StaticResource overlayLabelVisibilityConverter }">
                   <Binding ElementName="passwordBox" Path="IsKeyboardFocusWithin" />
                   <Binding ElementName="passwordBox" Path="SecurePassword" />
                   <Binding ElementName="passwordBox" />
        </MultiBinding>
</Label.Visibility>

Would be nice it it could become something like this, removing the converter class:

  <Label.Visibility>
            <MultiBinding Converter="**{calcBinding:Binding '!passwordBox.IsKeyboardFoucsWithin and passwordBox.SecurePassword'** }">
                  <Binding ElementName="passwordBox" Path="IsKeyboardFocusWithin" />
                  <Binding ElementName="passwordBox" Path="SecurePassword" />
                  <Binding ElementName="passwordBox" />
             </MultiBinding>
 </Label.Visibility>

This probably involve the management of ElementNames.
Do you think it is feasible? I can help out if this is considered helpful.

Thank you.

I really appreciate the effort you put in CalcBinding and i'm aware of the amount of work it is needed to keep a project going.

By the way pull requests are accumulating and new issues are not even being discussed.

If you don't have the time or inclination to support this project anymore, please consider to transfer the project to someone else.

We really need a few fixes :)

Hope to hear you
Thank you

I have the expression:

<TextBlock Text="{cb:Binding 'IsNew ? \'(new)\' : Name', Mode=OneWay}"  />

But got the error:

System.Windows.Data Warning: 40 : BindingExpression path error: 'new' property not found on 'object' ''UserClientEditViewModel' (HashCode=48653125)'. BindingExpression:Path=nový; DataItem='UserClientEditViewModel' (HashCode=48653125); target element is 'TextBox' (Name=''); target property is 'Text' (type 'String')

When I remove the parentheses \'new\' then it works well.

I only seem to be able to use the '==' operator for comparing an enum.
Is it possible to use other operators such as '>='?

I tried this:
Visibility="{c:Binding 'CurrentUser.Level>=local:UserLevel.Administrator'}"
And got this error:
Binding error: calc converter can't convert expression{0}>=Enum1.Administrator: The binary operator GreaterThanOrEqual is not defined for the types 'MyNameSpace.UserLevel' and 'MyNameSpace.UserLevel'.

Using the equals operator is working though.

Theoretically I can support .net 4.0

hi , i really like the idea of your project , very helpful and time saver
i would like to add the feature of binding to enum values
like an enum with
element1,
element2,
element3

to bind like this
c:Binding path = property Is element1
please tell me if it's possible

First, i dont want to use decimal? type for every of my field...

So, in my datagridTextColumn, I have the following WORKING statement :

<DataGridTextColumn Header="MyValue" Binding="{conv:Binding '(MyValue==0?-1:MyValue)', StringFormat=C}" />

What it will do, is that when the binded property of the itemSource item is eqal to 0, it replace the 0 per -1. If not 0, then the normal value is shown.

HOWEVER, my real goal here is to show '-' if the value is zero. But I am unable to succeed, because of tons of parsing Error. here are my tries :

<DataGridTextColumn Binding="{conv:Binding '(ProchainCoutant==0?\'-\':ProchainCoutant)'}"/>

ERROR : MarkupExtension is not properly closed

<DataGridTextColumn Binding='{conv:Binding Path="(ProchainCoutant==0?\'-\':ProchainCoutant)"}'/>

ERROR : expected : "

in fact, my problem is that basically, I am just unable to set any quote (\') in my formula

I've come across what appears to be a bug when using multibindings with bool-to-visibility, where it reports binding errors for templates that shouldn't be applying (based on DataType). Here's code to repro:

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication1"
    xmlns:c="clr-namespace:CalcBinding;assembly=CalcBinding"
    Title="MainWindow" Height="350" Width="525">
<StackPanel>
    
    <ContentControl x:Name="contentControl" Content="{Binding}">
        <ContentControl.Resources>
            
            <DataTemplate DataType="{x:Type local:ClassSimple}">
                <TextBlock>I am ClassSimple</TextBlock>
            </DataTemplate>

            <DataTemplate DataType="{x:Type local:ClassComplex}">
                <GroupBox>
                    <TextBlock>I am ClassComplex: <TextBlock Visibility="{c:Binding 'SomeProperty || SomeProperty2'}" /></TextBlock>
                </GroupBox>
            </DataTemplate>
            
        </ContentControl.Resources>
    </ContentControl>

    <Button Content="ClassSimple" Click="Click_ClassSimple"/>
    <Button Content="ClassComplex" Click="Click_ClassComplex"/>
</StackPanel>    
</Window>

And in CodeBehind:

public class ClassSimple { }
public class ClassComplex { public bool SomeProperty { get; set; } public bool SomeProperty2 { get; set; } }

private void Click_ClassSimple(object sender, RoutedEventArgs e)
{
    contentControl.DataContext = new ClassSimple();
}

private void Click_ClassComplex(object sender, RoutedEventArgs e)
{
    contentControl.DataContext = new ClassComplex();
}

If you click "ClassSimple," all is as expected. But if you click "ClassComplex" then "ClassSimple," you'll get:

Binding error: one of source fields is Unset, return null
System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='<null>' MultiBindingExpression:target element is 'TextBlock' (Name=''); target property is 'Visibility' (type 'Visibility')

Oddly, if you remove the GroupBox in the ClassComplex template, the binding error goes away. Likewise, it goes away if you just bind to SomeProperty or SomeProperty2 (not both).

To calculate the visibilty of a control i'm using CalcBinding something like 'A?.B?.C > 0'.

I get a binding error saying "Value produced by BindingExpression is not valid for target property.; Value=''"

I also tried 'A != null and A.B != null and A.B.C > 0' but i can't get it to work.

So the question: is Null-conditional operator supported?
Is it null supported in comparisons?

Thanks

P.S. - A naive converter works just fine

public class CarouselVisibility : BaseConverter, IValueConverter
{
   public object Convert( object value, Type targetType, object parameter, CultureInfo culture )
   {
       var vm = value as ViewModel;
       return vm?.A?.B?.C?.Count > 0 ? Visibility.Visible : Visibility.Collapsed;
   }
   public object ConvertBack( object value, Type targetType, object parameter, CultureInfo culture )
   {
      throw new NotImplementedException();
   }
}

I have working Binging

<TextBlock Visibility="{Binding Source={x:Static myProp:Settings.BoolSetting}, Converter={StaticResource BooleanToVisibilityConverter}}" />

However, the CalcBinding fail

<TextBlock Visibility="{cb:Binding Source={x:Static myProp:Settings.BoolSetting}" />

with

System.NullReferenceException: Object reference not set to an instance of an object.
   at CalcBinding.Binding.NormalizePath(String path)
   at CalcBinding.Binding.ProvideValue(IServiceProvider serviceProvider)

I'm direly missing support for FallbackValue (from BindingBase), which should be used when the expression can't be compiled/evaluated/throws. Is it feasible to add?

Math, Colors, enough?

Hi @Alex141 ,

First off, I insanely LOVE your library! I have used it for several years!
Soon (within 1 month or so), I will have to port my app to UWP. I am a beginner at UWP.

Since both WPF and UWP use binding, I would assume porting it would be easy. But since there's a request for this for 1.5 years (CommunityToolkit/WindowsCommunityToolkit#1790), I'm asssuming it's waay more complicated than I think.

I will have to, one way or another, port this to uwp. Any pointers as to what complications I should expect?

Background:
I insanely hate UWP, but for the upcoming months (until WinUI gets to version 3.0), I don't have a choice. Long story short, I want to use win2d, and using Xaml Islands is just a sad joke.

Best,
John

I would like to use my custom converter inside the CalcBinding. A reason is that WPF Binding automatically listen to the PropertyChanged events, so I do not need to create a view model with the event subscribe and unsubscribe.

My idea is something like

<MultiBinding Converter="{cb:MultiBinding P0 and P1}" >
    <Binding Path="IsSomething"/>
    <Binding Path="MyEnumProperty" Converter="{StaticResource MyEnumToBoolConverter}"/>
</MultiBinding>

Or maybe P[0] and P[1] instead of P0 and P1.

Here is what I have:

<Window x:Class="MySuperApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:MySuperApp"
        mc:Ignorable="d"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        d:DataContext="{d:DesignInstance {x:Type dvm:DesignMainWindowViewModel}, IsDesignTimeCreatable=True}"
        xmlns:c="clr-namespace:CalcBinding;assembly=CalcBinding"
        Title="{Binding Title}"
        x:Name="this_" d:DesignWidth="1600" d:DesignHeight="900">

    <Window.Resources>

        <sys:Double x:Key="IconHeigh">55</sys:Double>
        <sys:Double x:Key="IconWidth">55</sys:Double>
...
    </Window.Resources>

and then :
<Path Stretch="Uniform" Fill="Black" Height="{c:Binding 'local:IconHeigh - 10'}" Data="M15,... ,2,0z" />
The binding expression is wrong - I can't figure out what it should be. Can you help please?

Hi,
the following Tooltip-Binding is throwing an xaml-error in visual-studio:

ToolTip="{c:Binding '(myValue>0 ? \'sentence one\' : \'sentence two\')'}"

"markup extension is not properly closed".

It's working fine in the app at runtime though.

How do i fix that?
Thanks!

I have a read-only property

public bool IsEmpty  { get { ... } };

<TextBlock Visibility="{cb:Binding IsEmpty}" />

But the CalcBinding fails with TwoWay or OneWayToSource binding cannot work on the read-only property 'IsEmpty'.

When I add set to my property (doing nothing), then it works OK.

I have a <ListBox> with <DataTemplate> and I need to bind Visibility to the condition, if the item is null or not. In a bare WPF I use

<TextBlock Text="Item is null" Visibility="{Binding Converter={StaticResource IsNullConverter}}" />

However, I would like to use a fancy CalcBinding, something like

<TextBlock Text="Item is null" Visibility="{cb:Binding '. == null'" />

How to denote the whole item in the expression (. is not working).

Hi Alex,

First off, insanely awesome lib! Been using it for more than a year now!
Having said that, when there's a LOT of databinding initializations, the startup is really slow.
I basically have a list of databound controls. For 240 controls, it takes roughly 10-12 seconds to startup.

Imagine this code:

foreach (var beat in model.music_beats) {
    var ctrl = new music_beat_ctrl { DataContext = beat, Height = ActualHeight};
    canvas.Children.Add(ctrl);
}

Each music_beat_ctrl is databound, more or less:

<materialDesign:PackIcon Kind="Link" RenderTransformOrigin="0.5,0.5" Width="18" Height="18" Margin="-9 0 0 0"
Visibility="{c:Binding 'linked or highlighted'}"
Foreground="{c:Binding 'highlighted ? media:Brushes.LightSeaGreen : media:Brushes.DimGray'}"
/>

<materialDesign:PackIcon Kind="GuitarElectric" Foreground="DimGray"
Width="{c:Binding 'type == local:beat_type.major ? 18 : 12'}"
Height="{c:Binding 'type == local:beat_type.major ? 18 : 12'}"
Opacity="{c:Binding 'type == local:beat_type.major ? 1 : 0.3'}"
ToolTip="{c:Binding 'type == local:beat_type.major ? 'Major Beat' : 'Minor Beat''}"
/>

While doing profiling, it seems to end up calling DynamicExpresso.Interpretor.constructor 960 times, which ends up with 28800 calls to DynamicExpresso.Interpretor.Reference - I would assume these should be able to be cached somehow?

I faced in issue in my project. When using a type which has defined implicit cast to bool in a property, binding visibility to that property doesn't work and conversion fails with following message:
System.InvalidCastException: Specified cast is not valid.

It happens because of explicit cast is called on value in BoolToVisibilityConverter.Convert:
if ((bool)value) return Visibility.Visible;

this test reproduces issue:

        [Test]
        public void DoesNotFailConvertingWhenValueHasImplicitConversionToBool()
        {
            Assert.DoesNotThrow(() =>
                new BoolToVisibilityConverter()
                .Convert(new CastableToBoolean(true), typeof(Visibility), null, CultureInfo.CurrentCulture));
        }

        private sealed class CastableToBoolean
        {
            private bool value;

            public CastableToBoolean(bool value = false)
            {
                this.value = value;
            }

            public static implicit operator bool(CastableToBoolean obj)
            {
                return obj.value;
            }
        }

I didn't find a way how to bind visibility with enum compare condition:
<WrapPanel Margin="5" Visibility="{c:Binding 'MyProperty==Value1'}">
Instead of Value1 I tried also MyEnumType.Value1, local:MyEnumType.Value1, nothing helps, everything result is 'Visible' with error:
System.Windows.Data Warning: 40 : BindingExpression path error: 'Value1' property not found on 'object' ''TabModel' (HashCode=42904806)'. BindingExpression:Path=local; DataItem='TabModel' (HashCode=42904806); target element is 'WrapPanel' (Name=''); target property is 'Visibility' (type 'Visibility')

Is it possible to use multibinding for different types of arguments?:

Content="{c:Binding Path='\'Points: \' + Points'}" 

where Points is int property.
It returns me error like:
Binding error: calc converter can't convert expression"Points"+{0}: Expression of type 'System.Int32' cannot be used for parameter of type 'System.Object' of method 'System.String Concat(System.Object, System.Object)'

WPF binding engine only takes the StringFormat property into account when the target property is of the String type. For properties of the Object type (like the BarStaticItem.Content property), the StringFormat property is ignored.
For instance this behavior in the standard Label control:

<Label Content="{Binding SomeProperty, StringFormat=This string will not be displayed}" />

Why I am looking may be there is some solution with your library.
Thanks.

I have a bool? property and bind it to Visibility:

Visibility="{cb:Binding 'IsConnected == null || IsConnected == false'}"

I got error Binding error: one of source fields is Unset, return null. Is it possible to work with nullable types?

Hi, It's a very useful library. Please add a version that supports Universal Windows Apps.
Thanks.

Error is returned:
'Binding' is not valid for Setter.Value. The only supported MarkupExtension types are DynamicResourceExtension and BindingBase or derived types

Great extension!

Please add support for 3.5!

I get an exception every time i forget to set Mode=OneWay for getter-only properties.
is it possible to autodetect such properties and automatically set binding Mode=OneWay?

When a design time view model is used visual studio show intellisense for the Path property for normal bindings.

Seems like they are not supported yet, just outside classe directly in the namespace

Such 'complex' property access shown as error in Resharper:
<Setter Property="IsEnabled" Value="{c:Binding !DataContext.IsRemoved}"/>
! pointed as not expected token.
And I can not ignore this line something like
<!-- ReSharper disable Xaml.BindingWithContextNotResolved -->
Only was is Disable Resharper Daemon for all file, but i don't like it much.

Is there some workaround?

Hi,
I can not use string methods, because I can not convert input object to string....
Non of the trials below does not work:

• using "System.": System.String(TxtVersion)).StartsWith('0')
• using "System:": System:String(TxtVersion)).StartsWith('0')

or can I use (in a different way)?

Create ability to set user custom Converters to c:Binding.

For Binding: if converter is defined then call it after source -> target binding and before target -> source binding
For MultiBinding: if converter is defined then call it after source -> target binding. (for multibinding we have one mode permanently)

In XAML the equals sign is an special character on attribute values.

How to write the following expression?

Visibility ="{c:Binding Value == null}"

Thanks

There is a bug in library dynamic expresso. Order of params, that transfer to Invoke() method should be the same as order of parameters, transfered to Interpreter.Parse() method, but is the same as the order in which the parameters are occured in the expression.
See example:

        var Parameter1 = new Parameter("a", typeof(int));
        var Parameter2 = new Parameter("b", typeof(int));

        var expr = new Interpreter().Parse("b-a", Parameter1, Parameter2);

        Console.WriteLine(expr.Invoke(1, 2));
        Console.ReadLine();

Expected: 1 (as a = 1, b = 2)
Real: -1 (b = 1, a = 2)

Because of this bug MathConverter can accept only such templates: {0}..{1}..{2} etc

Hi Alex,

Once again, I insanely love your lib! I wanted to start working on porting this to UWP, but I hit quite a few blockers.

For once, the idiots at UWP, don't have a "Visibility.Hidden" enum. Then, there's no Binding.Default. Those are the minor issues.

The big issues are : there's no IMultiValueConverter, and MarkupExtension is not implemented the same:
You're expecting
public override object ProvideValue(IServiceProvider serviceProvider)
but you get
public override object ProvideValue()

I didn't manage to figure out how to get a serviceProvider, and wasn't exactly sure what it was for, and long story short, there way too many issues.

I still hate UWP with all my heart, but unfortunately I need it , because of win2d.

So, I came up with a workaround, which is decent for me:

    public bool is_sel_hov => expression_value(is_selected || is_hovering, "is_selected || is_hovering", PropertyChanged);
    public string full_name => expression_value(user_name + " " + password, "user_name password", PropertyChanged);

Both is_sel_hov and full_name automatically trigger notification updates when is_selected/is_hoverint/user_name/password change.

It's not ideal, but for now it's enough for me.

Best,
John

I would like to use CalcBinding for TemplateBinding in Style definitrion, too. If it is already possible, add example to the README.md, thanks.
(Maybe using some kind of {TemplateBinding Separator, Converter=cb:CalcConverter ...}?)

As the same as

<TextBlock Text="{c:Binding '(1 == 2) ? 10 : 20'}" />

We may expect that

<TextBlock Text="Test" Foreground="{c:Binding '(1 == 1) ? #ff0000 : #000000'}" VerticalAlignment="Center"/>

display text in red.
Unfortanutelly, no text is displayed

Thank you :)

If i bind to MySubView.MyOtherProperty the expression is not reevaluated with the correct value of the property when its value changes.

CalcConverter.Convert is not even called. The binding just does not work.
I don't really have time to study the problem and submit a solution so please help me out.

Thank you.

A very important use case is to calculate based on the position of a component in a canvas. I don't see any support for this. Do you know the status of this?

I need to use (Canvas.Left) + Width + (some constant integer) and (Canvas.Top) + Height + (some constant integer) in my calculation.

The CalcBinding can not be set with:
myLabel.SetBinding(Label.ContentProperty, calcBinding);
because CalcBinding does not inherit BindingBase.
How can this be achieved?

enable using custom math methods:

Or is replaced to || even if or is a part of long named property, e.g. Coordinates. with "and" there is analog situation.

I think this library would do well with having automated test cases. The parser seems to not be perfect right now, (see #33). If I change something, I want to be sure I'm not breaking other functionality.

Add NotNullToVisibility behaviour so we can write just

<Button Visibility="{calc:Binding SelectedItem, Mode=OneWay}" />