App: Add option to restore database when a DB error occurs at startup

Elwig/Services/BackupService.cs

@@ -1,11 +1,13 @@
 using Elwig.Helpers;
 using Elwig.Helpers.Export;
+using Microsoft.Win32;
 using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
+using System.Windows.Input;
 
 namespace Elwig.Services {
     public static class BackupService {
@@ -106,5 +108,26 @@ namespace Elwig.Services {
                 } catch { }
             }
         }
+
+        public static async Task RestoreDatabase() {
+            try {
+                var d = new OpenFileDialog() {
+                    Title = "Datenbank wiederherstellen - Elwig",
+                    DefaultDirectory = App.Config.BackupPath,
+                    InitialDirectory = App.Config.BackupPath,
+                    DefaultExt = "sql.zip",
+                    Filter = "SQLite-Datenbank (*.sqlite3, *.sqlite3.zip, *.sql, *.sql.zip)|*.sqlite3;*.sqlite3.zip;*.sql;*.sql.zip",
+                };
+                if (d.ShowDialog() == true) {
+                    if (!InteractionService.AskContinue("Datenbank wiederherstellen", "Soll die Datenbank wirklich unwiederruflich durch die wiederhergestellte Version ersetzt werden?"))
+                        return;
+                    Mouse.OverrideCursor = Cursors.Wait;
+                    await App.ReplaceDatabase(d.FileName);
+                }
+            } catch (Exception exc) {
+                InteractionService.ShowException(exc);
+            }
+            Mouse.OverrideCursor = null;
+        }
     }
 }