WPF Namespace tag xxx doesnt exist in XML namespace

Question

I have the following in vb:

Namespace WpfSample

Class MainWindow
    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.

    End Sub
End Class



Public Class BooleanToVisibilityConverter
    Implements IValueConverter
    Public Sub New()

    End Sub

    Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert
        If value.Equals(True) Then
            Return System.Windows.Visibility.Visible
        Else
            Return System.Windows.Visibility.Collapsed
        End If
    End Function

    Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
        If value.Equals(System.Windows.Visibility.Visible) Then
            Return True
        Else
            Return False
        End If
    End Function
End Class
End Namespace

then my XAML looks like:

<Window x:Class="WpfSample.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:l="clr-namespace:WpfSample"
    Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
    <l:BooleanToVisibilityConverter x:Key="converter" />
    </Window.Resources>

    <Grid>
        <TextBox x:Name="txtName" HorizontalAlignment="Left" Height="23" Margin="112,37,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
        <Label x:Name="lblLabel" Content="{Binding Text, ElementName=txtName,UpdateSourceTrigger=PropertyChanged}" 
           Visibility="{Binding IsChecked,ElementName=chkShowLabel, Converter={StaticResource boolToVis}}"
           HorizontalAlignment="Left" Margin="256,37,0,0" VerticalAlignment="Top"/>
        <CheckBox x:Name="chkShowLabel" Content="Show Label" HorizontalAlignment="Left" Margin="112,65,0,0" VerticalAlignment="Top"/>

    </Grid>
</Window>

i am seeing the following 3 errors The name "BooleanToVisibilityConverter" does not exist in the namespace "clr-namespace:WpfSample".

The type 'l:BooleanToVisibilityConverter' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built.

The tag 'BooleanToVisibilityConverter' does not exist in XML namespace 'clr-namespace:WpfSample'.

Answer 1

remove the usage of converter from the sample and first build your project. Only after it gets build successfully will you be able to use it in xaml.

Also your key name under Window.resources is "converter" while you are using "boolToVis" in label tag

One more thing which you can do is after building the project by removing the converter usage in xaml, write xmlns:l= . Your full assembly name will appear in the list. This way you can avoid writing incorrect assembly path.