Call files, cancel call if webservice say so

With these it helps Once the request is made, you cannot tell the stage at which client would invoke abort - so its quite possible that the request has reached to server and server is already processing it. So even if you could abort from client side, server would already process the request. The same will be applicable in asynchronous web request. A full proof solution is to have compensating transaction i.e. in this case, abort should invoke call to server to delete the file (server should not raise an error if file does not exists).

wish helps you I am not a php guy but this might help you make a better decision: As you said you have two options:
Option 1: (Bad Idea) 1. User Clicks login button 2. A JavaScript method is called, which makes a Ajax Call to authentication service 3. If authenticated, you redirect user to Home page

This might help you This isn't perfect, but you could identify that "call" was pressed instead of "cancel" by listening for the UIApplicationSuspendedNotification (you'd have to add some logic to ignore this event when someone pushed the 'home' key, or was accepting an incoming call... maybe by adding/removing the observer around the logic where the phone number is being presented):

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(suspended:) name:@"UIApplicationSuspendedNotification" object:nil];

-(void)suspended:(NSNotification *) notification
{
    NSLog(@"Suspended");
}

it fixes the issue This is impossible. You can create a Task that will complete when that existing operation completes, or mark itself as cancelled if a cancellation token is cancelled, but that won't actually stop the original operation, merely allow the program to continue executing despite the fact that the operation isn't actually done yet.
See this blog article for more information on the subject.

With these it helps I have a Json file and an ajax call in Javascript file. Trying to write correct webservice method using Hello World asmx file template. What should I write in method in order to make it display/return/read json data on website? , Thats is the solution that worked for me:
[WebMethod]

public string HelloWorld() {

    using (StreamReader r = new StreamReader(@"C:\Users\data.json"))
    {

        string json = r.ReadToEnd();

        return json;

    }