Develop Reference

Alljoyn c# implementation for Windows 8

I've been playing with my Raspberry pi 2 with Windows 10 IoT. And want to send commands to device using alljoyn.
However I was unable to find any kind of client/router sample c# code.
Microsoft offers Windows.Devices.AllJoyn namespace only for Windows 10 :(
https://msdn.microsoft.com/library/windows/apps/windows.devices.alljoyn.aspx
Am I the only person who want to use alljoyn in c# app other than in Windows 10?

I've started a C# wrapper project here: https://github.com/dotMorten/AllJoynDotNet
Currently supports Windows Desktop, Windows 10, and Xamarin Android, but I don't see why a Windows 8.1 Store app wouldn't be possible as well - we just need the alljoyn_c.dll compiled for 8.1.

Windows phone store Query

We have an app which is built in Windows phone 8 silver light framework. As windows 10 is coming and we are trying to upgrade this app to Windows phone 8.1.
Our only concern is can we keep both version of the app on store? i.e on store we should be able to upload two different build for WP8 and WP8.1.
Let me know if you guys have the answer

Yes you can have two different versions in the store. But my question is if you do have a Windows Phone 8 version of an application why do you need the 8.1 version too, where WP8 application would support both the versions?
You could have a look at this, in order to migrate your app into Universal apps.

WP8/Win8 Store App - Sockets

Justed tried to add multiplayer support for a monogame project. I wanted to use libgren but as far as I could see there are no networking classes available on windows phone. Is there any workaround? How can send and recieve tcp and udp packets on windows phone? The same question applies to Windows 8 Store Apps.

There are sockets for Windows Phone 8.1 and Windows 8.1 - http://msdn.microsoft.com/en-us/library/windows/apps/windows.networking.sockets.aspx . If you are targeting WP8 (not 8.1) you will need to use the Silverlight Windows Phone 8 sockets - http://msdn.microsoft.com/en-us/library/windows/apps/hh202874(v=vs.105).aspx

Getting Windows Phone version and device name in Windows Phone 8.1 XAML

In Windows Phone 8 Silverlight I use
Environment.OSVersion.ToString()
to get Windows Phone version and
DeviceStatus.DeviceManufacturer+" "+DeviceStatus.DeviceName
to get device name.
These APIs no longer work with Windows Phone 8.1 XAML. I have found
Windows.Security.ExchangeActiveSyncProvisioning.EasClientDeviceInformation()
this seems to return the manufacturer and device name but OS is returned as just "Windows Phone".
Is there a way to get the exact Windows phone version?

This is currently not possible In Windows Runtime 8.1 (Phone and Windows). It does look like it might be planned thanks to Morten Nielsen and Pete Brown
EDIT: This is now possible in Windows 10. See this SO answer as well as this article for more useful features.

For 8.1, you can use this project on Github https://github.com/Microsoft/phone-info that includes an example application for retrieving both static and dynamic properties of a Windows Phone device.
For Windows 10, the APIs that were used to gather these data on (8 and 8.1) have changed. I have found one blog post https://www.suchan.cz/2015/08/uwp-quick-tip-getting-device-os-and-app-info/ for someone who has created a helper class that retrieves the following properties from a Windows 10 UWP app
current OS family - phone/desktop/...
current OS build number - 10.0.10240.16413
current OS architecture - x86/x64/ARM
current App Display Name
current App Version - 3.0.2.0
current Device manufacturer - Nokia
current Device model - Lumia 1520
In his post he shows how to get basic data about current device, operating system and application.
give it a try maybe it helps

In Windows Phone 8.1:
Windows.Security.ExchangeActiveSyncProvisioning.EasClientDeviceInformation().FriendlyName
It worked for me!

Detect OS version - Windows Phone 7 or Windows Phone 8?

I have an application for Windows Phone 7. I have created visual studio 2012 in windows 8 desktop. I am trying to use the application in Windows Phone 8 device also with some changes involved. How can I programmatically detect whether the device is Windows Phone 7 or Windows Phone 8?

Just as you would on any other platform with C#: Environment.OSVersion

You can use this toolkit to check the version of the phone:
http://mangopollo.codeplex.com/
bool IsWP8() : Returns if the phone running the application is a
Windows Phone 8
EDIT: If you don't want to use the whole toolkit here is how it checks it:
public static bool IsWP8 { get { return Environment.OSVersion.Version >= TargetedVersion; } }
private static Version TargetedVersion = new Version(8, 0);
Creds to original author.

You shouldn't need to.
Either it is a Windows Phone 7 app and will work on both Windows Phone 7 and Windows Phone 8 devices or it is a Windows Phone 8 application.
A Windows Phone 7 app running on Windows Phone 8 shouldn't be able to do anything that a Windows Phone 7 device shouldn't be able to do.

This article has some good strategies as well.
http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202996(v=vs.105).aspx
It is not just about run-time either, for example, your code may function one way on wp7 and another on wp8 depending on availability of an API. In this case a #define may the best way to go, because you really don't care what kind of device you are running on, but what SDK you were built against.