Question

I want use a external file to customize styles on my app, but it does not working. I am following this step-by-step but when I execute the project exception falls into:

A first chance exception of type ‘System.Windows.Markup.XamlParseException’ occurred in System.Windows.ni.dll

My XAML code:

app.xaml:

<Application.Resources>
    <local:LocalizedStrings xmlns:local="clr-namespace:App1" x:Key="LocalizedStrings"/>
    <ResourceDictionary x:Key="myDict">
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="Resources.xaml"/>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Application.Resources>

Resources.xaml:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <Style TargetType="TextBox" x:Key="MyTextBox">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0.5"/>
        <Setter Property="BorderBrush" Value="Gray"/>
        <Setter Property="Opacity" Value="0.5"/>
        <Setter Property="Foreground" Value="Red"/>
    </Style>

</ResourceDictionary>

Answer 1

Try moving your local resource declarations inside the ResourceDictionary that you’re creating and assigning to the Application.Resources property:

<Application.Resources>
    <ResourceDictionary x:Key="myDict">
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="Resources.xaml"/>
        </ResourceDictionary.MergedDictionaries>

        <local:LocalizedStrings xmlns:local="clr-namespace:App1" x:Key="LocalizedStrings"/>
        <!-- other resources in here -->
    </ResourceDictionary>
</Application.Resources>