x:Static in UWP XAML

Question

An app I'm working on requires a ConverterParameter to be an enum. For this, the regular way to do would be:

{Binding whatever, 
    Converter={StaticResource converterName}, 
    ConverterParameter={x:Static namespace:Enum.Value}}

However, the UWP platform x: namespace does not seem to have the Static extension.

Does anyone know if there's a solution that does not rely on x:Static for comparing an enum in binding?

Telophase

I haven't done any UWP, so I don't know, but there's this article explaining how to make a markup extension for Silverlight (which doesn't have x:Static either). It may apply here – Girth

Here's answer about using enum in xaml that must work – Whitmire

Answer 1

This works for me in a UWP:

<Button Command="{Binding CheckWeatherCommand}">
  <Button.CommandParameter>
     <local:WeatherEnum>Cold</local:WeatherEnum>
  <Button.CommandParameter>
</Button>

Basilica

Wow, this needs to be upvoted more. That works perfectly, no workarounds needed with classes and what not. – Fivefold

Is there any way to specify this in line via CommandParameter=..., to avoid the xaml in the button body? – Monmouth

@Monmouth Seems to work fine declaring the type as a resource. <local:WeatherEnum x:Key="Cold">Cold</local:WeatherEnum> then referenced anywhere CommandParameter={StaticResource Cold}. Not as clean as x:Static and inline but it saves adding the XAML wrappers everytime. – Wingate

I'm getting unable to cast .... to object of type .... error tooltip in XAML. And in runtime the value is null. – Multilingual

Answer 2

The most concise way I know of...

public enum WeatherEnum
{
    Cold,
    Hot
}

Define the enum value in XAML:

<local:WeatherEnum x:Key="WeatherEnumValueCold">Cold</local:WeatherEnum>

And simply use it:

"{Binding whatever, Converter={StaticResource converterName},
 ConverterParameter={StaticResource WeatherEnumValueCold}}"

Kernel

That doesn't work for me... I tried as you suggested, but on runtime I get this error: The TypeConverter for "Phase" does not support converting from a string. (Phase is my enumerator) – Selfcentered

This doesn't work me either. It throws a conversion error – Hypaethral

Answer 3

There is no Static Markup Extension on UWP (and WinRT platform too).

One of the possible solutions is to create class with enum values as properties and store instance of this class in the ResourceDictionary.

Example:

public enum Weather
{
    Cold,
    Hot
}

Here is our class with enum values:

public class WeatherEnumValues
{
    public static Weather Cold
    {
        get
        {
            return Weather.Cold;
        }
    }

    public static Weather Hot
    {
        get
        {
            return Weather.Hot;
        }
    }
}

In your ResourceDictionary:

<local:WeatherEnumValues x:Key="WeatherEnumValues" />

And here we are:

"{Binding whatever, Converter={StaticResource converterName},
 ConverterParameter={Binding Hot, Source={StaticResource WeatherEnumValues}}}" />

Savoury

Answer 4

This is an answer utilizing resources and without Converters:

View:

<Page
.....
xmlns:local="using:EnumNamespace"
.....
>
  <Grid>
    <Grid.Resources>
        <local:EnumType x:Key="EnumNamedConstantKey">EnumNamedConstant</local:SettingsCats>
    </Grid.Resources>

    <Button Content="DoSomething" Command="{Binding DoSomethingCommand}" CommandParameter="{StaticResource EnumNamedConstantKey}" />
  </Grid>
</Page>

---

ViewModel

    public RelayCommand<EnumType> DoSomethingCommand { get; }

    public SomeViewModel()
    {
        DoSomethingCommand = new RelayCommand<EnumType>(DoSomethingCommandAction);
    }

    private void DoSomethingCommandAction(EnumType _enumNameConstant)
    {
     // Logic
     .........................
    }

Grivet

Doesn't seem to work in WinUi3 for me. – Semivowel

Answer 5

In most situations, x:Bind is a drop-in replacement for x:Static, so you can do:

ConverterParameter="{x:Bind namespace:Enum.Value}}"

If you need x:Bind in a resource dictionary, you will need to give it a code-behind file: https://learn.microsoft.com/en-us/windows/uwp/data-binding/data-binding-in-depth#resource-dictionaries-with-xbind

Ambulance

Doesn't work if nexted in another {x:Bind} – Semivowel

@Semivowel If you are using x:Bind you dont need a converter, you can use a method binding with multiple parameters. – Ambulance

I'm trying to bind a radio button IsChecked property, I'm not sure how that could be done with a method binding. – Semivowel

@Semivowel Trying to bind it to what? – Ambulance

@Semivowel Did you look at this? learn.microsoft.com/en-us/windows/uwp/data-binding/… – Ambulance

I'm binding IsChecked from multiple radio buttons to a string property and using the converter parameter to identify which radio button should be checked. I wanted to switch from string to enum but could not find a way to send the enum as a converter parameter. {x:Bind} to function can be used for getting the value but BindBack does not allow sending extra parameters so there's no way to know from which radio button the boolean value is coming from. – Semivowel

Only solution I found currently is to create a separate BindBack method per radio button which works but is not really that clean as you now have multiple SomethingChecked methods in the view model which do very similar things and need to return a bool. – Semivowel

@Semivowel Have you tried using the RadioButtons control, which supports binding to an items source and a selected item? – Ambulance

@Semivowel learn.microsoft.com/en-us/windows/winui/api/… – Ambulance

This seems like a better option, thanks! – Semivowel

x:Bind only works in code-behind situations - at least in the newest WinUI - so it's really not a "drop-in replacement" – Haycock

@EmperorEto Not sure what you mean. – Ambulance

If you do an x:Bind in a XAML file that's not the code-behind of a Window or a UserControl - like a ResourceDictionary - it throws a compile error. XamlCompiler error WMC1119: This Xaml file must have a code-behind class to use {x:Bind}. See http://go.microsoft.com/fwlink/?LinkID=532920&clcid=0x409 for more information – Haycock

You can give your resource dictionary a code-behind file. – Ambulance

@EmperorEto See here: learn.microsoft.com/en-us/windows/uwp/data-binding/… – Ambulance

But yes, point taken, in some cases it's not just simple "drop-in". Updated answer. – Ambulance

Well whadaya know! I had no idea. Thanks much. – Haycock

RHGGHG. WinUI 3 SDK 1.5 - x:Bind requires the root element of your page to inherit from FrameworkElement or Window, but root type 'Microsoft.UI.Xaml.ResourceDictionary' does not – Haycock

Let us continue this discussion in chat. – Ambulance