Question

I am using a DatePicker from the WPFToolkit library in a UserControl I have defined in a ControlLibrary.

If I use my UserControl from another application I get an ApplicationException: “Cannot find type ‘Microsoft.Windows.Controls.DatePicker’. The assembly used when compiling might be different than that used when loading and the type is missing.”

I am able to avoid this exception if I add an assembly reference to WPFToolkit library from the Application that is referencing my UserControl. Is there a way for me to do this without having to reference the WPFToolkit assembly in my Application?

Here is the xaml for my UserControl:

<UserControl x:Class="View.DateRangeView"
             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:toolkit="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit"
             mc:Ignorable="d" 
             d:DesignHeight="50" d:DesignWidth="300">
    <UserControl.Resources>
        <ResourceDictionary Source="/ReuxablesLegacy;component/candy.xaml" />
    </UserControl.Resources>
    <Grid VerticalAlignment="Top">
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="Auto" SharedSizeGroup="enable" />
        </Grid.ColumnDefinitions> 

        <StackPanel Orientation="Horizontal" >
            <toolkit:DatePicker Margin="3" SelectedDate="{Binding Path=LowRange}" Width="100" />
            <TextBlock Text=" To " Margin="3" VerticalAlignment="Center" />
            <toolkit:DatePicker Margin="3" SelectedDate="{Binding Path=HighRange}" Width="100" />
        </StackPanel>
        <CheckBox Grid.Column="1" Content="Enable" Margin="3" VerticalAlignment="Center" IsChecked="{Binding Path=Enabled}" />
    </Grid>
</UserControl>

Answer 1

you have to add a reference to both your assembly and the 3rd party assembly to the application.