Add shared export infrastructure

LehrerApp.Desktop/Views/Workload/WorkloadEvaluationView.axaml

@@ -7,12 +7,14 @@
     <StackPanel Margin="20,16" Spacing="16">
 
       <!-- Zeitraum -->
-      <Grid ColumnDefinitions="Auto,Auto,Auto" HorizontalAlignment="Left">
+      <Grid ColumnDefinitions="Auto,Auto,Auto,Auto" HorizontalAlignment="Left">
         <ComboBox Grid.Column="0" ItemsSource="{Binding PeriodModeOptions}"
                   SelectedItem="{Binding PeriodMode}" Margin="0,0,8,0"/>
         <ComboBox Grid.Column="1" ItemsSource="{Binding MonthOptions}" SelectedItem="{Binding SelectedMonth}"
                   Margin="0,0,8,0" IsVisible="{Binding IsMonthMode}"/>
         <ComboBox Grid.Column="2" ItemsSource="{Binding YearOptions}" SelectedItem="{Binding SelectedYear}"/>
+        <Button Grid.Column="3" Content="Als CSV exportieren" Margin="16,0,0,0"
+                Click="OnExportClick"/>
       </Grid>
 
       <!-- Pflichtstunden (6.3.2) -->

LehrerApp.Desktop/Views/Workload/WorkloadEvaluationView.axaml.cs

@@ -1,8 +1,23 @@
 using Avalonia.Controls;
+using Avalonia.Interactivity;
+using LehrerApp.Desktop.Services;
+using LehrerApp.Desktop.ViewModels.Workload;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace LehrerApp.Desktop.Views.Workload;
 
 public partial class WorkloadEvaluationView : UserControl
 {
     public WorkloadEvaluationView() => InitializeComponent();
+
+    private async void OnExportClick(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not WorkloadEvaluationViewModel vm) return;
+        var topLevel = TopLevel.GetTopLevel(this);
+        if (topLevel is null) return;
+
+        var export = ExportFile.Csv("Arbeitszeitauswertung exportieren",
+            vm.ExportSuggestedFileName, vm.ExportCsv());
+        await App.Services.GetRequiredService<ExportService>().SaveAsync(topLevel.StorageProvider, export);
+    }
 }