Develop Reference

Best Approach to communicate between a Windows forms application written in C# and Native Android App

so our company wrote an accounting app,in windows,using c# for a certain company that ordered an accounting application.
after a while,they requested an android app that can communicate with the server and request or send data from or to the database that the windows form application uses,which uses SQLExpress 2014.
note that : the application that runs on the android platform may need run on more than one client at any given time.
AND
the android app will be native.
my main question is this : whats the best technology to use?
do i HAVE to use web services ?

well to do that i have to install IIS on the windows client which is
all im trying to avoid,because i have a setup and the program has been
mass produced within the city so i cant just take back every
customer's product and add iis setup procedures to the setup...if u
know what i mean
Not true. Since WCF days, there's an in-process option called XXX self-host which is a tiny web server written in C# and started along with your process using code.
Currently your best web should be developing your Web services using OWIN/Katana self-host and implement your RESTful service running on a Windows service (did you know about TopShelf?).
Check this interesting MSDN article to learn more about self-hosting a Web API into a Windows Service using Topshelf.
TL;DR
Your best bet here would be creating a Windows service which might be installed along with the Windows application or in some customer's server machine and host this way your RESTful Web service using ASP.NET Web API.
This is easy to deploy and distribute, and your customer won't require an IIS installed to host web services.

Why Host WCF Service in Worker Role

In the process of building my first AZURE based application using WCF services I have stumbled across a number of examples where people show how one can host a WCF Service inside a Worker Role.
Such as in these articles:
http://www.codeproject.com/Articles/188464/Host-WCF-Services-in-an-Azure-Worker-Role
http://code.msdn.microsoft.com/windowsazure/CSAzureWCFServices-20c7d9c5
Very simple question, can someone please explain what use case would require hosting a WCF service in a worker role? What are the motivation/advantages of doing this?

Hosting a WCF service inside of a WebRole implies that it is hosted within IIS. Some folks prefer to not have the footprint of IIS mess with their ServiceHost and host the service directly. They have more control over how the communication with their service is done without IIS in the middle.
Also, when shrink-wrapping the packaged solution for customers, it is simpler to create an installer package without trying to rely on IIS infrastructure that customers may or may not have properly deployed/configured.
HTH

What are the limitations , if any , when hosting a WCF service on azure

I wrote a WCF service and I want to host it in azure. When I wrote the service , I didn't have in my mind that I am going to host it in azure.
Every application , even a WCF service , is using platform resources. When I say resource , I mean anything:
memory
CPU
File handle
Low level APIs (pinvoke)
Com objects.
sockets
.Net BCL API (Yep , I even consider this as a resource)
Databases
etc..etc.. (anything that is not the code i have written myself)
Hypothetical example : If the service , for example , logs to Drive 'H' , it may work on my computer(since I have drive 'H') , but it will probably won't work on the cloud. Same for Drive 'C' , or any drive letter , I don't even know how a file system is seen from the service perspective.
This is just one example.
Another hypothetical example : I can pinvoke from the service some winapi method in nt.dll , It will work on my computer. But i guess it won't work on the cloud.
My question is :
How can I know what kind of resources can be used on the cloud and how resources are used when writing to the cloud? What are the "rules" to follow? Also Is there any "Smart" Compiler that can ensure that my service is compatible with the cloud platform
I'll be glad to get any detailed explanation or a reference\book about this topic. I tried to find some info by googling but didn't find anything that cover it well enough.
Once i'll get the details i'll be able to make the nessecary porting to my service (if any needed at all).

The limitations depend on how you host your WCF Service:
Windows Azure Web Sites: This is a shared hosting model. If you deploy your WCF service in a web site you'll need to take that into account. This means you'll have limited access to disk, limited access to low level APIs, no way to use native libraries, ...
Windows Azure Web / Worker Roles (PAAS): Your application will be deployed in a Windows Server 2008 / 2012 VM. So if you want, you can leverage all functionalities you would use on a normal Virtual Machine (all "resources" you mention in your question). The only thing to keep in mind is that these virtual machines are non persisent (meaning all data you store on them could get lost) and that the load balancer is not sticky (could be an issue if you use WCF sessions). The fact that these machines are not persistent also means you cannot install a database server on them in a reliably way, but you can use an external database, like SQL Azure. The advantage of this solution is that the machines are maintained by the Fabric Controller, so you push your service package (the application) to Windows Azure, and the rest of the deployment is done for you.
Windows Azure Virtual Machines (IAAS): You get a machine like in Web / Worker Roles which allows you to use all "resources", but with even more control. The machines are persistent, meaning everything you store on them is persisted in Blob storage (if the machine crashes, you don't loose the data stored on the OS drive and data disks). This is the closest alternative to an on-premises deployment, but this also adds extra work. It will be up to you to manage deployments on all servers, to handle security updates, ... But in this case you could install your own database on a machine. Keep in mind that also here the load balancer is not sticky which could impact features like WCF session.

You can follow below mentioned Guidance for Using WCF in Windows Azure.
Deciding whether to run a WCF service in a web or worker role
WCF services can be hosted in either a web role or a worker role. Which type of role you decide to use depends on the type of WCF service you are writing
Running a WCF service in a web role
A WCF service that is set up for deployment to a Windows Azure web role uses the same setup and configuration as a WCF service hosted in IIS on on-premise servers.
Understanding WCF Security in Windows Azure
The security concerns for hosting a WCF service on Windows Azure is the same as those you encounter hosting the service in on-premise servers
Troubleshooting WCF in Windows Azure
You can troubleshoot performance issues for WCF services in Windows Azure using the same techniques that you use with WCF services hosted on-premise servers
For get more information check Guidance for Using WCF in Windows Azure Here
I hope this will help to you.

iPhone, WMI, iis service

I am thinking about writing an application that will monitor IIS Service with iPhone, and send notification, perform resets if an IIS goes down.
I dont want to create a web service to do that but rather connect to a machine, specifying credentials and then get data from the IIS Service state.
Is it even possible?
Is it possible with iPhone?
I need to make this app generic enough for people to use with their hosted web sites and monitor their health and being able to reset it and/or recycle AppPools. I cant implement a service for any hosted environment. I need to be able to give the iPhone users an ability to connect to their host and once you are connected to the machine and authenticated to perform WMIs the phone users can mess with the iis. Is it possible?

I see your point not wanting to use web service because you want to monitor and reset IIS service, while web service is based on IIS. How about RestFul service? I have created RestFul service based on OWIN (Open Web Interface for .Net) and Kayak. Kayak may have some examples there.
The cool thing about those tools or lib is that the framework is very simple and does not rely on IIS. You can provide two URLs, one for get and one for post. The former is to get status of IIS server and post is to reset IIS. Those services can be just XML of JSON based objects and it will be up to the the OWIN service to do the job on the back end. Another great feature of this is that you can even create the service in a console app or any other ways (Windows service or Window Form in system tray) on WindowsXP or Home version. The app will provide RestFul service based on HTTP with specific port.
RestFul service is available for variety of platforms, including iPhone.

Although IIS supports remote administration I doubt there's a way to implement it on the iPhone easily.
You could write an actual Windows Server (not a web service) you could connect to with a socket which can do all the monitoring instead though.

.net web service hosted within my application

I'm migrating an old Delphi application that I wrote into C#. The application is a datalogger that exposes logged data requests via a SOAP web service interface.
The web service is contained with the delphi graphical windows application, i.e. no need to run a web server like IIS, etc I just run the application and it's up and running under the hood.
I'm looking to do the same in my c# Windows form application, I can find loads of resources on writing web services that are ultimately hosted within IIS but am struggling to find a solution for a self contained web service within my application.
Does anyone have any suggestions or can point me towards any resources on this?
The web service does not neceserily have to be SOAP, REST is fine (in fact probably prefered).

Look into WCF Services.
Hosting and Consuming WCF Services
Hosting WCF services in a Windows Forms Application

The System.Web.Hosting namespace allows you to host ASP.Net pages without using IIS within your applications. I have never used it to host web services but I found a tutorial that seems to provide a guide on doing this-
http://msdn.microsoft.com/en-us/magazine/cc163879.aspx

If you're wanting to host a service inside your application, it's possible with the System.ServiceModel.ServiceHost class. You need to learn WCF first, but that at least answers your question to get you started. If you have any further questions, leave me a comment or two and I'll update my answer to accommodate your inquiries.