CODEWITHSUNDEEP
wpfivalueconverter
VivekDev
VivekDev

Reputation: 25553

How to use specific properties of a Value converter in wpf xaml

I have a enum to string converter 

public class EnumToStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter,
        CultureInfo culture)
    {
        MailSettingsStateEnum enumValue = (MailSettingsStateEnum)value;

        // extension method on the enum, to return a string based on enum.
        return enumValue.Description(); 
    }

    // ConvertBack not relevant here.
}

I am using this in wpf xaml easily as follows to set the Content property of a label.

<Label Content="{Binding MailSettingState, Converter={StaticResource 
EnumConverterString}}" 
BorderBrush="{Binding MailSettingState, Converter={StaticResource 
EnumConverterBorderBrush}}" />

Now as you can see, I have another property BorderBrush. I also have to set this based on the same enum. And so I had to write another converter EnumConverterBorderBrush

So is there a way by which I have only one converter, and it return an object which has two properties and i can use these properties in the xaml? I can create the converter, its easy, but I dont know how to use it in xaml. Say the converter returned an object and has tow property called MessageString(of type string), and another BorderBrush of the type Brush, how do I use it the xaml?

Upvotes: 2

Views: 3566

Answers (3)

ASh
ASh

Reputation: 35720

converter should return object which match requested targetType. converter can return different values for input enum value depending on parameter. I think it is more flexible than relying on targetType only.

public class SpecEnumConverter: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is Enum)
        {                
            if ((string) parameter == "brush")
                return "Red"; // return brush here!

            // if not pre-defined parameter (null or any other), return description
            return (int) value; // return enum description here!
        }
        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

usage:

<Label Content="{Binding MailSettingState, Converter={StaticResource 
EnumConverterSpec}}" 
BorderBrush="{Binding MailSettingState, Converter={StaticResource 
EnumConverterSpec}, ConverterParameter='brush'}" />

Upvotes: 1

aksu
aksu

Reputation: 1847

I already commented above, but here's the solution.

<Label DataContext="{Binding MailSettingState, Converter={converters:EnumConverter}}" Content="{Binding Label}" BorderBrush="{Binding BorderBrush}"/>

public class EnumConverter: MarkupExtension, IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var enumValue = (MailSettingsStateEnum) value;
        return new ConvertedEnum { Label = enumValue.Description(), 
                                   BorderBrush = new BorderBrush()};

    }

    // ConvertBack not relevant here.

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }
} 

public class ConvertedEnum
{
    public string Label {get; set;}
    public BorderBrush {get; set;}
}

Separate converters still look prettier to me.

Upvotes: 1

Arcturus
Arcturus

Reputation: 27065

You can switch the output based on the targetType you receive in your converter.

So you could do something like this:

public class EnumToStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter,
        CultureInfo culture)
    {
        var enumValue = (MailSettingsStateEnum)value;

        switch(targetType)
        {
            case typeof(string)
                return enumValue.Description(); 
            case typeof(Brush)
                return enumValue.GetBrush();
            default:
                throw new NotSupportedException("Type not supported")
        }
    }

    // ConvertBack not relevant here.
}

Now you'll have one converter to rule them all!

Upvotes: 2

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