PropertiesWindow.xaml

<Window x:Class="WeatherExternalDataProvider.PropertiesWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:ignore="http://www.galasoft.ch/ignore"
        mc:Ignorable="d ignore" Background="Black" SizeToContent="Height" Width="256" ResizeMode="NoResize"
        Title="Weather Settings" x:Name="Me" WindowStartupLocation="CenterOwner">
    <Window.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="/vMixControllerSkin;component/MainSkin.xaml"/>
            </ResourceDictionary.MergedDictionaries>
            <XmlDataProvider IsInitialLoadEnabled="True" Source="https://pogoda.yandex.ru/static/cities.xml" x:Key="Cities" XPath=".//country"/>
        </ResourceDictionary>
    </Window.Resources>
    <StackPanel Margin="2">
        <TextBlock Style="{StaticResource PropertyName}">Country</TextBlock>
        <ComboBox x:Name="country" ItemsSource="{Binding Source={StaticResource Cities}}" DisplayMemberPath="@name" SelectedValuePath="@name" SelectedValue="{Binding Provider.Country, Mode=TwoWay, ElementName=Me}"/>
        <TextBlock Style="{StaticResource PropertyName}">City</TextBlock>
        <ComboBox ItemsSource="{Binding SelectedItem, ElementName=country}" SelectedValuePath="@id" SelectedValue="{Binding Provider.City, Mode=TwoWay, ElementName=Me}"/>
        <StackPanel Margin="0,2,0,0" HorizontalAlignment="Right" Orientation="Horizontal">
            <Button Margin="2,0" IsCancel="True">Cancel</Button>
            <Button IsDefault="True" Click="Button_Click">Ok</Button>
        </StackPanel>
    </StackPanel>
</Window>