Develop Reference

Why does the Xamarin.Forms designer not show windows layouts?

I tried searching for this everywhere, but I cannot find any solution.
I also tried looking at solution properties, project properties, visual studio preferences, Visual Studio extensions, change XAML xmlns definitions but I have no clue why this is not possible, and I think it should be standard simple functionality.
When you create a new Xamarin.Forms project that includes
, you would suspect that there is not only a way to see your XAML design on Android and iOS but also for any Windows platform you are targeting, such as W10 Desktop but also other Windows platforms that UWP supports and that supposedly Xamarin. Forms do support according to the website from Microsoft. You can easily build your project for these platforms, no problem. But I want to see what I am doing before I compile my work.
When opening your XAML design, instead of a simple Android / iOS and Windows tab in the design panel, Windows is nowhere to be found.
How am I supposed to see how my Windows screen is going to look without an option to see this? In WPF and plain UWP, this works fine, but somehow for Xamarin it only shows Android/IOS, but apparently, Xamarin has full support for Windows (desktop).
I am looking for multi-platform support to create a windows desktop application that is easily portable to iOS and Android. I thought Xamarin could do that, but if I am not able to see what I am doing on Windows in terms of layout, how am I supposed to develop a solid UI for the platform?
I am probably missing some kind of checkbox somewhere (I am hoping), but I cannot find any information about this. Yes, I tried to google. And Stack overflow. And Xamarin documentation from Microsoft. And watch YouTube videos about Xamarin for 20 minutes that supposed to explain the Xamarin multi-platform support. And after 20 minutes I find they only specifically explain iOS/Android but nothing about Windows. So yeah, getting pretty tired of searching and hope someone can be kind enough to help me out.

This is a limitation of Xamarin.Forms. Although it uses XAML, it has a custom XAML dialect which is not compatible with WPF/UWP, so the built-in UWP designer cannot handle it directly and it will require a custom designer implementation.
But if you want a first-class Windows development experience compatible with Android, iOS and even WebAssembly, try looking into the Uno Platform. This is a UWP bridge with full XAML compatibility with UWP XAML, so your app will look exactly the same on all platforms and provides full templating and styling support. In addition, Uno Platform provides bridge for many non-UI APIs as well, including things like Clipboard, Accelerometer and so on. In the end you will be able to just write a Windows app which will work everywhere with minimal changes.
You can use XAML adaptive triggers to make sure the app works well on each screen size and scales great from desktop to mobile.

If you want desktop version of you app just add UWP or WPF blank project to your solution.
For UWP it goes like this:
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/platform/windows/installation/
For WPF it goes like this:
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/platform/other/wpf
Right click on your "Project.UWP" or "Project.WPF" project and pick "Set as Startup Project"
and building your solution.

Change app root frame in Windows Phone 8.1 Silverlight application

I have two simple questions since I'm very new to Windows Phone programming:
1:
How do I cange the root frame, or show a different Page on startup, in a Windows Phone 8.1 Silverlight application? I have a LoginPage and then I want to check if the user is logged in show MainPage as root frame and if the user is not logged in show the LoginPage.
2:
Windows Phone Silverlight applications seems so different to me compared to the Windows Phone WinRT applications, or maybe I'm just not experienced enough. For example I can't put a placeholder/hint text in a textBox in Silverlight but it's super easy in WinRT, why is it like that? Isn't that something very basic that many IDE's implements? Or have I missed something mayor when I'm developing a Silverlight application for Windows Phone?
I know that Windows Phone WinRT is used to create universal apps and Silverlight is used to create only mobile apps for Windows Phone, but why is developing a mobile app in Silverlight so much different (at least to me) compared to build a Windows Phone app i WinRT?

For your first question, use the UriMapper.
The basic principle is that you check if the user is logged in or not and based on that, navigate to the correct view.
The code is not all that complicated, there is a very good tutorial up on Shawn Kendrot his blog here...
For question 2, how to add some sort of hint/watermark can be done in several different ways.
But a very simple version is presented on MSDN here... it uses events to set and clear the watermark.

Point 1
You have to go to Package.appxmanifest and under the tab called Application the second field contains the startup page name. Currently it should be MainPage.xaml, just change it to LoginPage.xaml.
Point 2
I don't quite understand your question. Silverlight and Windows Runtime are two different platforms, they have in fact many different libraries. The goal of Windows Runtime is to run the same application on several different devices, so different hardware requirements and different resolutions. It was a need to organize the environment differently and of course Microsoft added some minor changes such as the hint text (e.g.).
What is so different to you? I did the porting of an app from SL to WinRT but it's not difficult nor tricky at all.

Windows Phone Silverlight/Xaml Which one i choose for developing my application [duplicate]

When I create new Windows Phone project I have an option to create a "Windows Phone" or "Windows Phone Silverlight" app. I know that they have different runtimes and different APIs.
I was under the impression that Microsoft wants to unify Windows and Windows Phone platforms so why is there even a Silverlight version? What benefits does it bring?
Also, if I want to create an app just for Windows Phone and never have plans to bring it to Windows, what should I choose, Silverlight or Windows Phone?

I'd suggest you go with "Windows Phone" (non-Silverlight). It's the new API, which works for both Windows and Windows Phone. At some point you may want to port the app or create a new one for Windows and you'll already know the API (and porting will be way easier). Also, the new API will most likely get more updates and features added, and at some point you may even be forced to update to it (either because the old one is no longer supported, or because it does not have some features that you need).
As it was said in the other answers - the Silverlight option is there only for backward compatibility and is likely to be phased out in time. That is - it's good if you already know the API and have many libraries (yours or others) for WP Silverlight, but if you're just starting - you'd better go for the new technology.
Edit
There is one other thing to consider before choosing between the two types of apps. Some features are only available in a Silverlight app, and others (smaller amount) - only in a Xaml app. Here's an article with some info on the differences: Migrating your Windows Phone 8 app to a Windows Runtime XAML app

Windows RT Xaml is quite new and People have to generate some knowledge first.
Silverlight for phone has been around for years and there's a load of tools available: Phone Toolkit, diverse Controls, etc.
Just killing it off would have hurt many developers who built up intellectual property over a long time forcing them to start over.
When starting a project with Silverlight you will have more things around that help you get stuff done.
When starting with WinRT Xaml, you will have better performance, but will have to figure a lot out by yourself.
So the Silverlight option is there to not throw of Silverlight developers.
I recently started a new project on WinRT Xaml and my experience was that I had to recreate a lot of common tools like Caches, etc. But also a lot of things that were in Toolkits previously are now part of the platform itself. Also, when moving over to Windows 8, you get to share a lot of code which is nice.

Unifying the environment(s) would be ideal. In my opinion, it hasn't been very successful. At one point in time, you could only develop under Silverlight, so what you are seeing is just a newer version of the same thing to keep backwards compatibility as well as to keep Silverlight's developers happy. In the future, it will probably be phased out. Plus if you want to support older Phones, Silverlight is basically your only choice (you'll be surprise, how many WP users haven't updated their 8.0 to 8.1)
There really isn't any other real benefit of Silverlight other than maybe the Windows Phone Toolkit which has been tremendously useful (you can see how many SO's answers rely on this simple addon). Once the universal runtime gets fleshed out to the point where the documentation reflects what's actually available -- then I think it would be the default project for developing in Windows going forward.
If you're just starting, I would use Silverlight the knowledge based is much greater. After you get use to the WP environment then switch to runtime.

Apply Microsoft Office's theme to my windows application

Is it possible to implement theme of Microsoft Office in my windows application.
I mean when anyone changes theme of Microsoft Office it should also make change the theme of my windows application.
If its possible, let me know how to do that?

I do not think that what you're asking here is quite possible. Then again I may be wrong. As far as I know, the only way to use Microsoft Office-like visual styles with your application is either by using a third party application or creating the custom controls yourself (wouldn't recommend that, hours of coding and designing). In other words, you would be better off using a suite like DevExpress, but please be aware that it is not free.
Here's a result of an application implementing these controls (taken from the developer's website):
I'm sure if you make a Google search, you could possibly find free alternatives to this software.

Style my .Net desktop application GUI with Silverlight/windows phone-style controls

I am writing my first vb.net application ( But I will tag c# here as well, as I am sure even a c# person can answer this with the similar .net implementation).
Short Description of my Applicaiton:
My desktop application will run on win platform only, using vb.net, it is a simple internet cafe management software, with a server gui running on server, and a client gui running on workstations, both communicating with TCP/IP to allocate time to customers, and the server storing some data in either xml files ( for human operators login info e.g) or in a small database. Nothing complicated.
What I would like to do:
I'd like to have a "sexy" look, i.e. either silverlight look or win7 phone look, yet this is a desktop application. I'd like to use CSS but its entirely optional, if there is a simple way to have my controls look like below without CSS thats fine with me.
What I have tried
I have looked into just doing a silverlight out of browser app, but as I am new to .net, and even though I have read up as many articles about using silverlight5 out of browser, I don't want to be caught down the road when I want to implement a feature and realize "Oh silverlight out of box doesnt support that".
So my question is , how do I implement one of the new looks in the picture in my desktop vb app?

You should look at using WPF for your application instead of using WinForms.
WPF (Windows Presentation Foundations) is a platform which works same way as silverlight but on desktop (as far as you need to be aware now.) Silverlight is a cut down version of WPF so WPF will give you a lot more controls and a lot more control over the program.
WPF uses XAML to draw up the UI and it holds the code in the source code file associated to the xaml file. If you have experience using Silverlight you should easily be able to make programs with WPF.
WPF is really powerful and gives you access to all the styling that is possible on Silverlight. WinForms is more so restricted which makes it harder to abandon the consistent Windows look and make your own intuitive and innovative UI.
Hope it helps!
Here are some tutorials if you are interested:
WPF Tutorials
Here is an example WPF desktop app (exact same look as achievable with Silverlight)

You can use wpf with Mahapps Metro : http://mahapps.com/MahApps.Metro/