WPF绑定以控制可见性“数字不是有效的枚举值”

Question

I am trying to set up the visibility property on a control so that it is visible when the bound value is matches an arbitrary value.

I have set up my converter as a static resource

Applied the binding

<Button Content="Foo" Visibility="{Binding SelectedValue, Converter={StaticResource ValueToVisibilityConverter}, ConverterParameter='1,2'}" />

But am met with the error

Error 1 '{Binding SelectedValue, Converter={StaticResource ValueToVisibilityConverter}, ConverterParameter='1,2'}' cannot be used as a value for 'Visibility'. Numbers are not valid enumeration values.

My converter code is

public class ValueToVisibilityConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter,System.Globalization.CultureInfo culture)
        {
            if (value == null || parameter == null || !(value is String))
                return Visibility.Collapsed;

            var currentValue = value.ToString();
            var matchStrings = parameter.ToString();
            var found = false;

            foreach (var state in matchStrings.Split(','))
            {
                found = (currentValue == state.Trim());

                if (found)
                    break;
            }

            return found ? Visibility.Visible : Visibility.Collapsed;
        }

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

The error stops compile and feels like it is trying to be too clever and is ignoring my converter.

Have I applied it wrong or am otherwise ignorant of some process going on.

EDIT:

To get the converter as a static resource I have the below in my window definition

xmlns:myConverters="clr-namespace:<namespace>;assembly=<assemblyname>"

And this in my window resources, right along side the same code for other converters that work perfectly

<myConverters:ValueToVisibilityConverter x:Key="ValueToVisibilityConverter" />

Answer 1

This is the code that should work.

<Button Content="Foo" 
        Visibility="{Binding SelectedValue, 
                     Converter={StaticResource ValueToVisibilityConverter}, 
                     ConverterParameter=1|2}" />

Things that you need to do

1. Values in ConverterParameter are passed without any quotes. So remove single quotes from converter parameter.

2. There is nothing stopping your from sending more than one value into the parameter, as long as you have a delimiter to separate them out later, but you cannot use a comma as that delimits the XAML. So use pipe in such cases and in converter split parameter by pipe | .

Moreover, please note that
a) There has to be a static resource for converter like this in resources.

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

where local is xmlns:local="Your project in which this converter is defined"

Note: A trick eBay used to use in urls, years ago, was to delimit data in the URL with QQ. A double-Q does not naturally occur in text data. If you ever get stuck for a text delimiter that will avoid encoding issues just use QQ... This will not work with split though (which requires single characters, but nice to know) :)

Answer 2

you can pass the ConverterParameter like

  <Binding Path="MyProperty"
             Converter="{StaticResource IntToBoolConverter}">
        <Binding.ConverterParameter>
            <sys:Int32>0</sys:Int32>
        </Binding.ConverterParameter>
    </Binding>