Windows Store-app with login-screen - xaml

Question

I need my program to start up with an login-screen, but I can not figure out how to make it look pretty.
I tried with a code, that looks like the following, but I do not think it is the "true way" to do it
<Page.Resources>
<Grid Style="{StaticResource LayoutRootStyle}">
<TextBlock x:Name="pageTitle" Grid.Column="1" Text="{StaticResource AppName}" Style="{StaticResource PageHeaderTextStyle}"/>
</Grid>
<TextBlock HorizontalAlignment="Left" Margin="647,31,0,0" Grid.Row="1" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top"/>
<TextBox HorizontalAlignment="Left" Margin="634,62,0,0" Grid.Row="1" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top"/>
<TextBlock HorizontalAlignment="Left" Margin="647,128,0,0" Grid.Row="1" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top"/>
<TextBox HorizontalAlignment="Left" Margin="634,167,0,0" Grid.Row="1" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top"/>
<Button Content="Button" HorizontalAlignment="Left" Margin="632,243,0,0" Grid.Row="1" VerticalAlignment="Top"/>
Can anybody tell me how to create a pretty login-screen as start-screen
I have though of a dialog, as it should not be possible to go back to it, but how can I create it with an empty background?
UPDATE
Thanks to DanielRozo in his answer below, my code now looks like this
<Popup IsOpen="True" Margin="200" Height="260" Width="900">
<Grid Height="250">
<TextBlock Style="{StaticResource HeaderTextStyle}" Text="Login" Margin="0" HorizontalAlignment="Center" VerticalAlignment="Top" Height="50" />
<TextBlock Style="{StaticResource ResourceKey=SubheaderTextStyle}" Text="" Margin="0,63,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" />
<TextBox Name="InputUsername" Margin="0,63,0,0" HorizontalAlignment="Right" Height="40" Width="650"/>
<TextBlock Style="{StaticResource ResourceKey=SubheaderTextStyle}" Text="" Margin="0,138,0,0" HorizontalAlignment="Left" VerticalAlignment="Top"/>
<PasswordBox Name="InputPassword" Margin="0,0,138,0" HorizontalAlignment="Right" VerticalAlignment="Top" Height="40" Width="650" />
<Button Name="Login" Content="" Margin="200,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Bottom" />
<Button Name="Cancel" x:Uid="LoginPopupCancel" Content="" Margin="300,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Bottom" />
</Grid>
</Popup>
But it does not work, when I rotate the screen, so I created this question
I also needs help to figure out how to set the page to a login-page

Answer 1

How about using the Popup class? I think it's a better approach of what you want. Something like:
<Popup Margin="200" IsOpen="True">
<Grid Margin="0" Height="322" Width="865">
<TextBlock Text="App Name Login" Style="{StaticResource HeaderTextStyle}" Margin="252,4,200,266"></TextBlock>
<TextBlock Text="User" Style="{StaticResource ResourceKey=SubheaderTextStyle}" Margin="244,63,498,223"/>
<TextBox x:Name="user" Margin="440,62,180,216"></TextBox>
<TextBlock Text="Pass" Style="{StaticResource ResourceKey=SubheaderTextStyle}" Margin="244,137,498,149"/>
<TextBox x:Name="pass" Margin="440,138,180,138"></TextBox>
<Button Name="Login" Content="Login" Margin="613,230,0,54"></Button>
<Button Name="Cancel" Content="Cancel" Margin="489,230,0,54"></Button>
</Grid>
</Popup>

Answer 2

Actually, I'd highly suggest the Web Auth Broker. If the user is auth'd using their LiveID, the WAB will provide you that credential, allowing you to not have to have credential re-entry for connected accounts. :)

Answer 3

I know that you've already marked another question as answer, but if you need to log in users into your app I think you should definitely take a look at the SplashScreen API. Overriding the default splashscreen, you'll have the users being always prompted with the username/password fields every time the app starts; moreover, you can never go back to the splashscreen, which is exactly what you say you need.
You should look at this sample: http://code.msdn.microsoft.com/windowsapps/Splash-screen-sample-89c1dc78 . I also suggest you to download Evernote from the market: trying an app made with the Splashscreen API may give you a better idea of what I'm saying.