We Keep Coding

How to Draw chart in windows phone 8 or 8.1 without using external library?

How can I can draw a simple chart in Windows Phone 8 or 8.1 without using an external library, I want to use C# + XAML code only.
I searched for a free library to do that on Windows Phone 8.1 (universal app) but I couldn't find any. All libraries I've found supported Windows Phone 8 or 7, not Windows Phone 8.1.

I made in answer in this similar question How to do Chart on Windows Phone Universal App
It might be able to help you. Telerik has an API that costs money and Google have a free one where you can get Charts through http requests. Check my reply - you might wanna use one of these. My answer is not about drawing it through XAML / C# which can be quite comprehensive.
To Draw it yourself through code you probably wanna create a Custom Control. Here is a few links to get you started:
http://code.msdn.microsoft.com/windowsapps/WPF-Line-Graph-Basics-033dd90e
http://msdn.microsoft.com/en-us/magazine/ee291567.aspx

Using the default tools is very hard, you can use telerik controls, though

WP8 Check if app has update

I want to implement a notification for user to update the app.
So how can I check if my application has an update (or newer version) on the store?
Edit: what I am looking for is a build-in api

You can find a XAML behavior that checks for updates in the WpWinNl toolkit. Here is a blogpost by Joost Van Schaik on how to implement it:
http://dotnetbyexample.blogspot.com/2013/09/zero-lines-of-code-solution-for-in-app.html

Here is a solution targeted to Windows Phone 8 using Cimbalino Windows Phone Toolkit:
http://developer.nokia.com/community/wiki/Application_update_prompt_using_Cimbalino_Windows_Phone_Toolkit
Edit: simpler solution without any toolkits http://developer.nokia.com/community/wiki/Checking_for_updates_from_inside_a_Windows_Phone_app

Where is ProgressRing Control?

I am trying to write a Windows Phone 8 SDK-based application. I keep seeing mention of a ProgressRing control but I don't see it in the Toolbox or in the xaml designer.
How do I use this?

ProgressRing is part of the Win8 UI controls, not WP8. In WP8 you should use SystemTray.ProgressIndicator instead which is part of the windows phone UI shell. See here and here for samples.

See below blog link for simple copy&paste code to exactly replicate the Windows ProgressRing (uses the actual style code). Works perfectly, just added it to my WP8 project:
http://briandunnington.github.io/progressring-wp8.html
There is more info about adapting it to WP8 in the answer to this question:
How to Use ProgressRing in Windows Phone 8
Download this app for your phone to see it in action.

ProgressRing is not available for Windows Phone 7 or 8, you have to use ProgressBar or rather the PerformanceProgressBar:
http://www.windowsphonegeek.com/articles/WP7-PerformanceProgressBar-in-depth

How can I use the Typography.NumeralAlignment Property on a WP7 textblock?

I have a text block that should display numbers in this format
This is supposed to be accomplished via Typography.NumeralAlignment property set to "Tabular" but how do I apply this to a Textblock in a Windows Phone 7 application.

This is only supported in SL5 and WP7.1 is based on SL4. I don't know of alternatives, sorry.
http://msdn.microsoft.com/en-us/library/system.windows.documents.typography.numeralalignment(v=vs.95).aspx
To get this to work in SL4, you will need to essentially implement it yourself..

How to create Silverlight 4 user control for windows phone app?

Can I create a silverlight user control that will work on a windows phone silverlight?
Is there a way to do so? I don't need very complex things. just a very simple user control with a label and a few text boxes.

Yes and yes. Here is a link for starters. If you scroll to the bottom you will see supported version info. And yes, user controls are supported for Silverlight for Windows Phone v 7.0
Just above the version info is also a clear, straightforward example of the simple kind of user control that you're interested in creating.
Cheers.

Sure you can as long as Controls you are using in Custom Control are also supported in Silverlight for WP7. in MSDN doc there is description of which Version of Silverlight supports it with weather its available in WP7. Also in doc every Method, Property ,Event ,etc has an icon in front of it. which will tell if its available in WP7 or not.