添加的本地资源未显示在WPF页面中

Question

I have this simple WPF page in which I am adding a local resource, which has its definition in Page's backend file.

<Page x:Class="WindowsSampleApplication.ValueConverter"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:WindowsSampleApplication"
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
    Title="ValueConverter">
    <Page.Resources>
        <local:YesNoToBooleanConverter x:Key="YesNoToBooleanConverter" />
    </Page.Resources>

    <Grid>
        <StackPanel Margin="10">
            <TextBox Name="txtValue" />
            <WrapPanel Margin="0,10">
                <TextBlock Text="Current value is: " />
                <TextBlock Text="{Binding ElementName=txtValue, Path=Text, Converter={StaticResource YesNoToBooleanConverter}}"></TextBlock>
            </WrapPanel>
            <CheckBox IsChecked="{Binding ElementName=txtValue, Path=Text, Converter={StaticResource YesNoToBooleanConverter}}" Content="Yes" />
        </StackPanel>
    </Grid>
</Page>

and this is the backend file for Page

namespace WindowsSampleApplication
{
    public partial class ValueConverter : Page
    {
        public ValueConverter()
        {
            InitializeComponent();
        }
        public class YesNoToBooleanConverter : IValueConverter
        {
            public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
            {
                switch (value.ToString().ToLower())
                {
                    case "yes":
                        return true;
                    case "no":
                        return false;
                }
                return false;
            }

            public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
            {
                if (value is bool)
                {
                    if ((bool)value == true)
                        return "yes";
                    else
                        return "no";
                }
                return "no";
            }
        }
    }
}

I have properly included namespace WindowsSampleApplication in Page level and the same namespace has definition for my resource. But am getting below error when added that local resource

I've just started with WPF tutorials from here but only thing I was trying rather than following tutorial was I added a Page instead of Window since I have created a Window already with earlier demos given there and hopefully I have converted everything that a Page needs to have instead of Window . Anyone have idea on how to resolve this issue?

UPDATE

I've also tried wrapping <local..../> withing <ResourceDictionary> as I ready it in SO, but wasn't of much use and error still remained as it is.

Answer 1

Since it looks like you are just trying out WPF, and you put the converter in the codebehind for no special reason, I would recommend the usual way for creating converters:

Create a new directory Converters in your WindowsSampleApplication project. Then add a new class file for each converter...

Now you know where to find your converters, and can easily reuse them.

PS: It's possible to put the converter in the codebehind as a nested class, but you should have a really good reason to do it. ( Binding converter as inner class? )

Answer 2

I think yout problem is that you have nested your converter inside ValueConverter page.

[EDIT]

There is no possibility of instantiate nested classes so the only option will be to declare converter class directly in WindowsSampleApplication namespace.

Updated code

namespace WindowsSampleApplication
{
    public partial class ValueConverter : Page
    {
        public ValueConverter()
        {
            InitializeComponent();
        }
        //Removed from here
    }
    public class YesNoToBooleanConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            switch (value.ToString().ToLower())
            {
                case "yes":
                case "oui":
                    return true;
                case "no":
                case "non":
                    return false;
            }
            return false;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value is bool)
            {
                if ((bool)value == true)
                    return "yes";
                else
                    return "no";
            }
            return "no";
        }
    }
}

Answer 3

You need to declare YesNoToBooleanConverter directly in the namespace. From MSDN: XAML and Custom Classes for WPF

Your custom class must be public and support a default (parameterless) public constructor. (See following section for notes regarding structures.) Your custom class must not be a nested class. Nested classes and the "dot" in their general CLR usage syntax interfere with other WPF and/or XAML features such as attached properties.

Link:

https://msdn.microsoft.com/en-us/library/ms753379(v=vs.100).aspx