// Сетка с полями авторизации

<Grid FocusManager.FocusedElement="{Binding ElementName=UsernameTxtBox}">
        <materialDesign:Card VerticalAlignment="Center" HorizontalAlignment="Center" Width="200" Height="200">
            <Grid>
                <Border Background="#3A404D"
                        BorderThickness="0,1,0,0">
                    <StackPanel Grid.Row="1" Orientation="Vertical" HorizontalAlignment="Center"
                                VerticalAlignment="Top" Margin="0,10,0,0">
                        <TextBox x:Name="UsernameTxtBox" Width="150" Margin="0,5"
                                 materialDesign:HintAssist.Hint="Username"
                                 Text="{Binding UserName, UpdateSourceTrigger=PropertyChanged}">
                            <TextBox.InputBindings>
                                <KeyBinding Command="{Binding LoginCommand}" Key="Return"/>
                            </TextBox.InputBindings>
                        </TextBox>
                        <PasswordBox x:Name="Password" Width="150" Margin="0,5"
                                 materialDesign:HintAssist.Hint="Password"
                                 local:PasswordBoxAssistant.BoundPassword="{Binding Path=Password, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                                 local:PasswordBoxAssistant.BindPassword="true">
                            <PasswordBox.InputBindings>
                                <KeyBinding Command="{Binding LoginCommand}" Key="Return"/>
                            </PasswordBox.InputBindings>
                        </PasswordBox>
                        <Button Content="Login" Margin="0,10,0,0"
                                Command="{Binding LoginCommand}"/>

                        <Button Content="Create an account" Margin="0,10,0,0"
                                Style="{StaticResource AccountButton}"
                                Command="{Binding RegisterPageCommand}"/>
                    </StackPanel>
                </Border>
            </Grid>
        </materialDesign:Card>
    </Grid>

// авторизация
private async Task<bool> Login()
        {
            try
            {
                var user = new UserModel();
                var users = new List<User>();
                var chats = new List<ChatModel>();

                using (var database = new MessengerContext())
                {
                    chats = database.Chats.ToList();

                    user = await database.Users.FirstOrDefaultAsync(u => u.Name == UserName && u.Passhash == Password);

                    user.LastLogin = DateTime.Now.ToString();
                    user.LastIP = IPGetter.GetLocalIPAddress();
                    database.Entry(user).State = EntityState.Modified;

                    Email = user.Email;

                    if (user.ProfilePicture != null)
                    {
                        BitmapImage image = new BitmapImage();
                        image.BeginInit();
                        image.StreamSource = new MemoryStream(user.ProfilePicture);
                        image.EndInit();

                        ImagePhoto = image;
                    }

                    await database.SaveChangesAsync();
                }

                if (users != null && user != null)
                {
                    var names = chats.Select(c => c.Name);
                    users = await chatService.LoginAsync(user.Name, Avatar());

                    users.ForEach(u =>
                    {
                        if (names.Contains(u.Name))
                        {
                            Participants.Add(new Participant
                            {
                                Name = u.Name,
                                Photo = user.ProfilePicture
                            });
                        }
                    });

                    UserMode = UserModes.Chat;
                    IsLoggedIn = true;
                }

                return true;
            }
            catch
            {
                dialogService.ShowNotification("Correct your input!");

                return false;
            }
        }