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Identifying the call that is connected to me via transfer Tapi3

I have been able to create an application that (ab)uses TAPI3Lib and understands incoming calls, puts them on hold, rings an internal number, connects the line that is on hold with the target number.
Below is the code getting the caller number
private void tapi_ITTAPIEventNotification_Event_Event(TAPI3Lib.TAPI_EVENT TapiEvent, object pEvent)
{
try
{
switch (TapiEvent)
{
case TAPI3Lib.TAPI_EVENT.TE_CALLNOTIFICATION:
TAPI3Lib.ITCallNotificationEvent cln = pEvent as TAPI3Lib.ITCallNotificationEvent;
if (cln.Call.CallState == TAPI3Lib.CALL_STATE.CS_OFFERING)
{
string c = cln.Call.get_CallInfoString(TAPI3Lib.CALLINFO_STRING.CIS_CALLERIDNUMBER);
string target = cln.Call.Address.DialableAddress;
.
.
.
Here i run a MSSQL query to a database to identify who is the owner of the number. and i display a form on screen with the potential user that is calling. A button on the form allows you to ring internal numbers (this action automatically adds the current line on hold.
IEnumCall ec = ia[line].EnumerateCalls();
uint arg = 0;
ITCallInfo ici;
try
{
ec.Next(1, out ici, ref arg);
ITBasicCallControl bc = (ITBasicCallControl)ici;
bc.Hold(true);
}
catch (Exception exp)
{
System.Windows.Forms.MessageBox.Show("May not have any call to put on hold!\n\n" + exp.ToString(), "TAPI3");
}
IEnumCall ec1 = ia[line].EnumerateCalls();
uint arg1 = 0;
ITCallInfo ici1;
try
{
ec1.Next(1, out ici1, ref arg1);
ITBasicCallControl bc1 = ia[line].CreateCall("107",TapiConstants.LINEADDRESSTYPE_IPADDRESS, TapiConstants.TAPIMEDIATYPE_AUDIO);
bc1.Connect(false);
}
catch (Exception exp)
{
System.Windows.Forms.MessageBox.Show("Target looks unreachable!\n\n" + exp.ToString(), "TAPI3");
}
This part connects the current active line with the line on hold;
ITBasicCallControl callOnHold = null;
ITBasicCallControl callConnected = null;
IEnumCall enumCall = ia[line].EnumerateCalls();
ITCallInfo callInfo;
uint dummy = 0;
while (true)
{
enumCall.Next(1, out callInfo, ref dummy);
if (callInfo == null)
return;
if (callInfo.CallState == CALL_STATE.CS_HOLD)
callOnHold = (ITBasicCallControl)callInfo;
else if (callInfo.CallState == CALL_STATE.CS_CONNECTED)
callConnected = (ITBasicCallControl)callInfo;
if (callOnHold != null && callConnected != null)
break;
}
callOnHold.Transfer(callConnected, true);
callConnected.Finish(FINISH_MODE.FM_ASTRANSFER);
The initiation is as follows;
ITAddress[] ia = new TAPI3Lib.ITAddress[10];
...
try
{
tobj = new TAPIClass();
tobj.Initialize();
IEnumAddress ea = tobj.EnumerateAddresses();
ITAddress ln;
uint arg3 = 0;
lines = 0;
cn = new callnotification();
tobj.ITTAPIEventNotification_Event_Event += new TAPI3Lib.ITTAPIEventNotification_EventEventHandler(cn.Event);
tobj.EventFilter = (int)(TAPI_EVENT.TE_CALLNOTIFICATION |
TAPI_EVENT.TE_DIGITEVENT |
TAPI_EVENT.TE_PHONEEVENT |
TAPI_EVENT.TE_CALLSTATE |
TAPI_EVENT.TE_GENERATEEVENT |
TAPI_EVENT.TE_GATHERDIGITS |
TAPI_EVENT.TE_REQUEST);
for (int i = 0; i < 10; i++)
{
ea.Next(1, out ln, ref arg3);
ia[i] = ln;
if (ln != null)
{
lines++;
}
else
break;
}
}
catch (Exception e)
{
System.Windows.Forms.MessageBox.Show(e.ToString());
}
--Scenario
CallA: Incoming Call
CallB: Internal Call
Operator: The main answering operator
Bob: A user of this application
Alice: The caller of CallA
Bob uses his cellphone to call Alice's call center. The Operator sees a pop-up screen containing Bob's name and number and then picks up the phone. (CallA is stored). Bob requests to talk to Alice. The Operator clicks on "Alice" on the screen (CallA is now on Hold and the Operator's phone creates CallB which rings Alice's phone). Alice answers the line and agrees to take the call. The Operator clicks "Transfer" on screen and CallA and CallB are connected.
--End of Scenario
--Expected result
When the Operator calls Alice, the event sees that 100 called 107 (with 100 being the Operator's address on the PBX and 107 Alice's. When the Operator connects the 2 calls, I want to be able to pop-up the same screen that the Operator got that includes the information of the connected caller. What am i missing in order to fire that event? Because when i try to check the cln.Call.get_CallInfoString(TAPI3Lib.CALLINFO_STRING.CIS_CALLERIDNUMBER) all i see is 100 which is the Operator that called Alice and that is correct. What is the check i need to do in order to identify that a call has been transferred thus → get the caller ID → pop up the screen
--End of Expected result
I wish i was able to describe it as i have it mind. Thank you for your time and excuse me for the lengthy post.

The TAPI3 lib may have a bit different naming but the fields you are looking for are called ConnectedId, RedirectingId and RedirectionId on TAPI itself.
But it is very dependent on the PBX itself whether these fields get filled or not.
In a transfered call scenario "theoretically" you should see this in the call information:
caller id: source of the original call (= the customer)
called id: destination of the original call (= the published number of the company or service)
connected id: the actual current other party (= who you are speaking with)
redirecting id: the number that transferred the call to you (= operator extension)
redirection id: the number the redirecting party (= operator) transferred the call to, which "should" be the device you are observing this from (if no further forwarding was involved)
But none of this enforced by TAPI so a PBX can fill in what it wants, and different vendors will :(

Following Kris Vanherck's suggestion, I did a temporary measure to handle the transfers until we figure out a proper solution;
string con="000";
while (con.Length ==3 && con.Length >=3)
{
con = cln.Call.get_CallInfoString(TAPI3Lib.CALLINFO_STRING.CIS_CONNECTEDIDNUMBER);
}
Silly approach but hey it works. Can't wait to see a more appropriate way to do this. Again thanks Kris for the direction.

You're making it too hard on yourself. You don't need to call Hold manually, the Transfer Method does it for you.
When a new call from B comes in (TAPI_EVENT.TE_CALLNOTIFICATION), you can take its ITBasicCallControl to call Transfer on:
case TAPI_EVENT.TE_CALLNOTIFICATION:
ITBasicCallControl incomingCall = callNotification.Call;
break;
The Transfer Method takes a pointer to a new created call for consultation, so make sure you create a new call before hand:
//In this case address is of type ITAddress and represents the operators address.
ITBasicCallControl consultationCall = address.CreateCall("107", TapiConstants.LINEADDRESSTYPE_PHONENUMBER, TapiConstants.TAPIMEDIATYPE_AUDIO);
Now you can call Transfer:
incomingCall.Transfer(consultationCall, false);
Finally, when the consultation call disconnects, and Alice wants to take the call, use the Finish Method to finish transfering:
case CALL_STATE.CS_DISCONNECTED:
ITBasicCallControl consultationCall = (ITBasicCallControl )callStateEvent.Call;
consultationCall.Finish(FINISH_MODE.FM_ASTRANSFER);
break;

Using MutationObserver in GeckoFx with C#?

I am using GeckoFx to perform a login to a specific website. This website edits the page with new information should the login fail (or require additional authentication, such as a ReCaptcha). Unfortunately, it is vital that I have access an event when the page is updated. I have tried numerous approaches mainly
A continual check if the uri is still the same upon each login attempt and a subsequent check on the specific element in question (to see if the display: none property was changed. (This resulted in an infinite loop as it seems GeckoFx updates the page in a nonblocking way, causing the program to go into an infinite loop)
Sleeping for ~5 seconds between login requests and using the aforementioned uri check. All this did (predictably, I was grasping at straws) was freeze the browser for 5 seconds and still fail to update the page
Searching the GeckoFx codebase for a specific event when the page is updated similar to the DocumentCompleted event (no such luck).
The most common approach I have read about (and one that makes the most sense) is to use a MutationObserver. It seems that all of the answers across the internet involve injecting Javascript in order to perform the requisite task. Seeing as all of my programming background has not touched web development whatsoever, I'm trying to stick to what I know.
Here is my approach so far, unfortunately, it is not much.
public class GeckoTestWebLogin
{
private readonly string _user;
private readonly string _pass;
public GeckoWebBrowser Gweb;
public Uri LoginUri { get; } = new Uri("https://website.com/login/");
public bool LoginCompleted { get; private set; } = false;
public bool Loaded { get; private set; } = false;
public GeckoTestWebLogin(string user, string pass)
{
_user = user;
_pass = pass;
Xpcom.EnableProfileMonitoring = false;
Xpcom.Initialize("Firefox");
//this code is for testing purposes, it will be removed upon project completion
CookieManager.RemoveAll();
Gweb = new GeckoWebBrowser();
Gweb.DocumentCompleted += DocLoaded;
//right about here is where I get lost, where can I set a callback method for the observer to report back to? Is this even how it works?
MutationObserver mutationObserver = new MutationObserver(Gweb.Window.DomWindow, (nsISupports)Gweb.Document.DomObject);
}
private void TestObservedEvent(string parms, object[] objs)
{
MessageBox.Show("The page was changed # " + DateTime.Now);
}
public void DocLoaded(object obj, GeckoDocumentCompletedEventArgs e)
{
Loaded = true;
if (Gweb.Url != LoginUri) return;
AttemptLogin();
}
private void AttemptLogin()
{
GeckoElementCollection elements = Gweb.Document.GetElementsByTagName("input");
foreach (GeckoHtmlElement element in elements)
{
switch (element.Id)
{
case "username":
element.SetAttribute("value", _user);
break;
case "password":
element.SetAttribute("value", _pass);
break;
case "importantchangedinfo":
GeckoHtmlElement authcodeModal =
(GeckoHtmlElement)
Gweb.Document.GetElementsByClassName("login_modal").First();
if (authcodeModal.Attributes["style"].NodeValue != "display: none")
{
InputForm form = new InputForm { InputDescription = "Captcha Required!" };
form.ShowDialog();
elements.FirstOrDefault(x => x.Id == "captchabox")?.SetAttribute("value", form.Input);
}
break;
}
}
elements.FirstOrDefault(x => x.Id == "Login")?.Click();
}
public void Login()
{
//this will cause the DocLoaded event to fire after completion
Gweb.Navigate(LoginUri.ToString());
}
}
As stated in the above code in the comments, I am completely lost at
MutationObserver mutationObserver = new MutationObserver(Gweb.Window.DomWindow, (nsISupports)Gweb.Document.DomObject);
I can't seem to find anything in GeckoFx's source for MutationObserver that would allow me to set a callback/event/whathaveyou. Is my approach the correct way to go about things or am I left with no options other than to inject Javascript into the page?
Much appreciated, thank you in advance.
Here is my attempt at option 2 in Tom's answer:
(Added into GeckoTestWebLogin)
public void DocLoaded(object obj, GeckoDocumentCompletedEventArgs e)
{
Loaded = true;
if (Gweb.Url != LoginUri) return;
MutationEventListener mutationListener = new MutationEventListener();
mutationListener.OnDomMutation += TestObservedEvent;
nsIDOMEventTarget target = Xpcom.QueryInterface<nsIDOMEventTarget>(/*Lost here*/);
using (nsAString modified = new nsAString("DOMSubtreeModified"))
target.AddEventListener(modified, mutationListener, true, false, 0);
AttemptLogin();
}
MutationEventListener.cs:
public delegate void OnDomMutation(/*DomMutationArgs args*/);
public class MutationEventListener : nsIDOMEventListener
{
public event OnDomMutation OnDomMutation;
public void HandleEvent(nsIDOMEvent domEvent)
{
OnDomMutation?.Invoke(/*new DomMutationArgs(domEvent, this)*/);
}
}

I don't think Geckofx's webidl compiler is currently advanced enough to generate the callback constructor.
Option 1. - Enhance MutationObserver source.
You could modify MutationObserver source manually to add the necessary constructor callback. Then recompile Geckofx. (I haven't look to see how difficult this is)
Option 2. - Use old style Mutation events.
public class DOMSubtreeModifiedEventListener : nsIDOMEventListener
{
... // Implement HandleEvent
}
Then something like (maybe in DocumentCompleted event handler):
_domSubtreeModifiedEventListener = new DOMSubtreeModifiedEventListener(this);
var target = Xpcom.QueryInterface<nsIDOMEventTarget>(body);
using (nsAString subtreeModified = new nsAString("DOMSubtreeModified"))
target.AddEventListener(subtreeModified, _domSubtreeModifiedEventListener, true, false, 0);
Option 3. - Use Idle + Check.
Add an winforms Application.idle event handler - and examine the document, to know when its ready.
Option 4. - Inject a javascript callback.
(As you have already mentioned) - This example is waiting until after a resize is done.
basically inject: "<body onresize=fireResizedEventAfterDelay()>" : then inject something like this:
string fireResizedEventAfterDelayScript = "<script>\n" +
"var resizeListner;" +
"var msDelay = 20;" +
"function fireResizedEventAfterDelay() {" +
"clearTimeout(resizeListner);" +
"resizeListner = setTimeout(function() { document.dispatchEvent (new MessageEvent('resized')); }, msDelay);" +
"}\n" +
"</script>\n";
Then in the C#:
browser.AddMessageEventListener("resized", (s) => runafterImDone())

Why is a List<Session> getting additional sessions from a later run

I am using fiddlercore to capture session information to run a compare on the data in a particular response. One of the things I am noticing that I don't understand is that I am getting session information from the second environment into the List collection I have for the first.
public class ManageCompares
{
public static string _test2BaseURL = "https://test2/";
public static string _dev1BaseURL = "http://dev1/";
private void RunCompares(string email, string handler, Reporting report)
{
ManageProcess.ShutDownProcess("iexplore");
RunExports exportTest2 = new RunExports();
RunExports exportDev1 = new RunExports();
string password = "d";
List<Session> oAllSessions_Test2 = exportTest2.RunExportGeneration
(email, password, _test2BaseURL, handler);
ManageProcess.ShutDownProcess("iexplore");
List<Session> oAllSessions_Dev1 = exportDev1.RunExportGeneration
(email, password, _dev1BaseURL, handler);
exportTest2.ExtractResponse(oAllSessions_Test2, handler, report);
//report.SetEnvironment2Body(ManageExports.ExtractResponse
// (oAllSessions_Dev1, handler, report, report.Environment2));
if (report.Test2ResponseCode != 500 && report.Dev1ResponseCode != 500)
{
bool matches = CompareExports.CompareExportResults
(report.Environment1Body, report.Environment2Body);
if (matches)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("Exports matched");
Console.ResetColor();
}
else
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("Export does not match");
Console.ResetColor();
report.GenerateReportFiles();
}
}
else
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine
("A exception was returned. Please review the log file.");
Console.ResetColor();
}
}
}
public class RunExports
{
public List<Session> RunExportGeneration
(string email, string password, string baseUrl,
string handlersUrlwithParams)
{
IWebDriver driver = new InternetExplorerDriver();
FiddlerApplication.Startup(8877, FiddlerCoreStartupFlags.Default);
List<Session> oAllSessions = new List<Session>();
LoginPage login = new LoginPage(driver);
FiddlerApplication.AfterSessionComplete += delegate(Session oS)
{
Monitor.Enter(oAllSessions);
oAllSessions.Add(oS);
Monitor.Exit(oAllSessions);
};
try
{
driver.Navigate().GoToUrl(baseUrl);
login.LoginToView(email, password);
driver.Navigate().GoToUrl(baseUrl + handlersUrlwithParams);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
finally
{
FiddlerApplication.Shutdown();
driver.Quit();
}
return oAllSessions;
}
}
List oAllSessions_Test2 and List oAllSessions_Dev1 are my two collections. When I debug the capture I typically see 15 rows in the oAllSessions_Test2 collection. Then after capturing oAllSessions_Dev1 I see the count has jumped up 14 or 15 and when I look at what is contained by the colleciton some of the Dev1 captures are now in there. oAllSessions_Dev1 has just the sessions I am expecting. I am guessing there must be a pointer someplace I am not expecting but I am stumped at this point how to clear it up. The other thing that I am noticing is that the session counter continues to increment while the application is cycling through the various cases.
I am also using Selenium WebDriver and IE to initiate the browser session but I don't think that is particularly relevant to this particular issue.
So what am I missing here?

Do this :
SessionStateHandler tAction = oS =>
{
Monitor.Enter(oAllSessions);
oAllSessions.Add(oS);
Monitor.Exit(oAllSessions);
};
FiddlerApplication.AfterSessionComplete += tAction;
......
//at the end before your return statement:
FiddlerApplication.AfterSessionComplete -= tAction;
So here is what's going on.
this: FiddlerApplication.Startup(8877, FiddlerCoreStartupFlags.Default);
(this specifically) FiddlerApplication
is holding onto references in an external application (fiddler) and administrating them for you. When you += and add a delegate FiddlerApplication.AfterSessionComplete += tAction;, the fiddler application was adding this to the list of methods it calls when the AfterSession event fires.
Because it's singleton (You are only dealing with one Fiddler application instance in your code), every time you do a += it adds it to the same list. This list in the FiddlerApplication doesn't get recreated every time you call your method. It's the same one that you called the first time, so even though your delegate falls out of it's scope declaration space (like local objects normally do in a method), the FiddlerApplication EventList maintains a reference to it and fires that delegate each time (and every other one).
So.....
In your method you create List<Session> oAllSessions = new List<Session>(); and access it in your delegate. This local variable is now passed back to the calling method, List<Session> oAllSessions_Test2 = exportTest2.RunExportGeneration.... and the delegate FiddlerApplication calls is the exact same list. So each time you call that method and the AfterSessionComplete fires, it updates the list even after it's been returned to the calling function.
To stop it you have to add: FiddlerApplication.AfterSessionComplete -= tAction; which tells the system "Hey, don't push updates to this method anymore. It's done receiving notifications."

In .NET languages class objects are passed by reference in almost all cases. If you assign an object reference to a variable, that variable will still refer to the original object. Changes to the original will be visible through all references. This is similar to how things used to happen in C/C++ when you stored pointers or references to structures in memory. The implementation details are different, but the results are the same.
Here's an example of what happens when you store list instances that might be changed later:
class ListTest
{
List<string> l = new List<string>();
public List<string> GetList() { return l; }
public void Add(string v) { l.Add(v); }
}
class Program
{
static void Main(string[] args)
{
ListTest t = new ListTest();
t.Add("a"); t.Add("b"); t.Add("c"); t.Add("d");
List<string> x1 = t.GetList();
List<string> x2 = t.GetList().ToList();
t.Add("e"); t.Add("f"); t.Add("g"); t.Add("h");
List<string> y1 = t.GetList();
List<string> y2 = t.GetList().ToList();
Console.WriteLine("{0}, {1}", x1.Count, y1.Count);
Console.WriteLine("{0}", string.Join(", ", x1));
Console.WriteLine("{0}", string.Join(", ", y1));
Console.WriteLine();
Console.WriteLine("{0}, {1}", x2.Count, y2.Count);
Console.WriteLine("{0}", string.Join(", ", x2));
Console.WriteLine("{0}", string.Join(", ", y2));
}
}
When you run that you get one set of identical results, because x1 and y1 are references to the same object. The second set of results are different because the call to ToList creates a new List<string> instance to hold the results.
This might be what is happening with the list that is returned by your Fiddler code.
--
Update after code review
What it looks like is that the delegate you're assigning to the AfterSessionComplete event is causing the code to treat oAllSessions as a static object bound to the event handler delegate. Various side-effects like this happen when you start playing around with code that generates closures and so on.
I would suggest changing the code to use a class method rather than an inline method - shift your oAllSessions variable and the code you're assigning to AfterSessionComplete out into the body of the class. That will at least establish whether the inline delegate is the cause of the problem.

Async XML Reading in Windows Phone 7

So I have a Win Phone app that is finding a list of taxi companies and pulling their name and address from Bing successfully and populating a listbox that is being displayed to users. Now what I want to do is, to search for each of these terms on Bing, find the number of hits each search term returns and rank them accordingly (a loose sort of popularity ranking)
void findBestResult(object sender, DownloadStringCompletedEventArgs e)
{
string s = e.Result;
XmlReader reader = XmlReader.Create(new MemoryStream(System.Text.UTF8Encoding.UTF8.GetBytes(s)));
String name = "";
String rName = "";
String phone = "";
List<TaxiCompany> taxiCoList = new List<TaxiCompany>();
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
if (reader.Name.Equals("pho:Title"))
{
name = reader.ReadInnerXml();
rName = name.Replace("&","&");
}
if (reader.Name.Equals("pho:PhoneNumber"))
{
phone = reader.ReadInnerXml();
}
if (phone != "")
{
string baseURL = "http://api.search.live.net/xml.aspx?Appid=<MyAppID>&query=%22" + name + "%22&sources=web";
WebClient c = new WebClient();
c.DownloadStringAsync(new Uri(baseURL));
c.DownloadStringCompleted += new DownloadStringCompletedEventHandler(findTotalResults);
taxiCoList.Add (new TaxiCompany(rName, phone, gResults));
}
phone = "";
gResults ="";
}
TaxiCompanyDisplayList.ItemsSource = taxiCoList;
}
}
So that bit of code finds the taxi company and launches an asynchronous task to find the number of search results ( gResults ) to create each teaxicompany object.
//Parses search XML result to find number of results
void findTotalResults(object sender, DownloadStringCompletedEventArgs e)
{
lock (this)
{
string s = e.Result;
XmlReader reader = XmlReader.Create(new MemoryStream(System.Text.UTF8Encoding.UTF8.GetBytes(s)));
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
if (reader.Name.Equals("web:Total"))
{
gResults = reader.ReadInnerXml();
}
}
}
}
}
The above snipped finds the number of search results on bing, but the problem is since it launches async there is no way to correlate the gResults obtained in the 2nd method with the right company in method 1. Is there any way to either:
1.) Pass the name and phone variables into the 2nd method to create the taxi object there
2.) Pass back the gResults variable and only then create the corresponding taxicompany object?

Right well there is a lot do here.
Getting some small helper code
First off I want to point you to a couple of blog posts called Simple Asynchronous Operation Runner Part 1 and Part 2. I'm not suggesting you actually read them (although you're welcome too but I've been told they're not easy reading). What you actually need is a couple of code blocks from them to put in your application.
First from Part 1 copy the code from the "AsyncOperationService" box, place it in new class file in your project called "AsyncOperationService.cs".
Second you'll need the "DownloadString" function from Part 2. You could put that anywhere but I recommend you create a static public class called "WebClientUtils" and put it in there.
Outline of solution
We're going to create a class (TaxiCompanyFinder) that has a single method which fires off the asynchronous job to get the results you are after and then has an event that is raised when the job is done.
So lets get started. You have a TaxiCompany class, I'll invent my own here so that the example is as complete as possible:-
public class TaxiCompany
{
public string Name { get; set; }
public string Phone { get; set; }
public int Total { get; set; }
}
We also need an EventArgs for the completed event that carries the completed List<TaxiCompany> and also an Error property that will return any exception that may have occured. That looks like this:-
public class FindCompaniesCompletedEventArgs : EventArgs
{
private List<TaxiCompany> _results;
public List<TaxiCompany> Results
{
get
{
if (Error != null)
throw Error;
return _results;
}
}
public Exception Error { get; private set; }
public FindCompaniesCompletedEventArgs(List<TaxiCompany> results)
{
_results = results;
}
public FindCompaniesCompletedEventArgs(Exception error)
{
Error = error;
}
}
Now we can make a start with some bare bones for the TaxiCompanyFinder class:-
public class TaxiCompanyFinder
{
protected void OnFindCompaniesCompleted(FindCompaniesCompletedEventArgs e)
{
Deployment.Current.Dispatcher.BeginInvoke(() => FindCompaniesCompleted(this, e));
}
public event EventHandler<FindCompaniesCompletedEventArgs> FindCompaniesCompleted = delegate {};
public void FindCompaniesAsync()
{
// The real work here
}
}
This is pretty straight forward so far. You'll note the use of BeginInvoke on the dispatcher, since there are going to be a series of async actions involved we want to make sure that when the event is actually raised it runs on the UI thread making it easier to consume this class.
Separating XML parsing
One of the problems your original code has is that it mixes enumerating XML with trying to do other functions as well, its all a bit spagetti. First function that I indentified is the parsing of the XML to get the name and phone number. Add this function to the class:-
IEnumerable<TaxiCompany> CreateCompaniesFromXml(string xml)
{
XmlReader reader = XmlReader.Create(new StringReader(xml));
TaxiCompany result = new TaxiCompany();
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
if (reader.Name.Equals("pho:Title"))
{
result.Name = reader.ReadElementContentAsString();
}
if (reader.Name.Equals("pho:PhoneNumber"))
{
result.Phone = reader.ReadElementContentAsString();
}
if (result.Phone != null)
{
yield return result;
result = new TaxiCompany();
}
}
}
}
Note that this function yields a set of TaxiCompany instances from the xml without trying to do anything else. Also the use of ReadElementContentAsString which makes for tidier reading. In addition the consuming of the xml string is much smoother.
For similar reasons add this function to the class:-
private int GetTotalFromXml(string xml)
{
XmlReader reader = XmlReader.Create(new StringReader(xml));
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
if (reader.Name.Equals("web:Total"))
{
return reader.ReadElementContentAsInt();
}
}
}
return 0;
}
The core function
Add the following function to the class, this is the function that does all the real async work:-
private IEnumerable<AsyncOperation> FindCompanies(Uri initialUri)
{
var results = new List<TaxiCompany>();
string baseURL = "http://api.search.live.net/xml.aspx?Appid=<MyAppID>&query=%22{0}%22&sources=web";
string xml = null;
yield return WebClientUtils.DownloadString(initialUri, (r) => xml = r);
foreach(var result in CreateCompaniesFromXml(xml))
{
Uri uri = new Uri(String.Format(baseURL, result.Name), UriKind.Absolute);
yield return WebClientUtils.DownloadString(uri, r => result.Total = GetTotalFromXml(r));
results.Add(result);
}
OnFindCompaniesCompleted(new FindCompaniesCompletedEventArgs(results));
}
It actually looks pretty straight forward, almost like synchonous code which is the point. It fetchs the initial xml containing the set you need, creates the set of TaxiCompany objects. It the foreaches through the set adding the Total value of each. Finally the completed event is fired with the full set of companies.
We just need to fill in the FindCompaniesAsync method:-
public void FindCompaniesAsync()
{
Uri initialUri = new Uri("ConstructUriHere", UriKind.Absolute);
FindCompanies(initialUri).Run((e) =>
{
if (e != null)
OnFindCompaniesCompleted(new FindCompaniesCompletedEventArgs(e));
});
}
I don't know what the initial Uri is or whether you need to paramatise in some way but you would just need to tweak this function. The real magic happens in the Run extension method, this jogs through all the async operations, if any return an exception then the completed event fires with Error property set.
Using the class
Now in you can consume this class like this:
var finder = new TaxiCompanyFinder();
finder.FindCompaniesCompleted += (s, args) =>
{
if (args.Error == null)
{
TaxiCompanyDisplayList.ItemsSource = args.Results;
}
else
{
// Do something sensible with args.Error
}
}
finder.FindCompaniesAsync();
You might also consider using
TaxiCompanyDisplayList.ItemsSource = args.Results.OrderByDescending(tc => tc.Total);
if you want to get the company with the highest total at the top of the list.

You can pass any object as "UserState" as part of making your asynchronous call, which will then become available in the async callback. So in your first block of code, change:
c.DownloadStringAsync(new Uri(baseURL));
c.DownloadStringCompleted += new DownloadStringCompletedEventHandler(findTotalResults);
to:
TaxiCompany t = new TaxiCompany(rName, phone);
c.DownloadStringAsync(new Uri(baseURL), t);
c.DownloadStringCompleted += new DownloadStringCompletedEventHandler(findTotalResults);
Which should then allow you to do this:
void findTotalResults(object sender, DownloadStringCompletedEventArgs e)
{
lock (this)
{
TaxiCompany t = e.UserState;
string s = e.Result;
...
}
}
I haven't tested this code per-se, but the general idea of passing objects to async callbacks using the eventarg's UserState should work regardless.
Have a look at the AsyncCompletedEventArgs.UserState definition on MSDN for further information.

Unique EventId generation

I'm using the Windows Event Log to record some events. Events within the Windows Event Log can be assigned a handful of properties. One of which, is an EventID.
Now I want to use the EventId to try and group related errors. I could just pick a number for each call to the logging method I do, but that seems a little tedious.
I want the system to do this automatically. It would choose an eventId that is "unique" to the position in the code where the logging event occurred. Now, there's only 65536 unique event IDs, so there are likely to be collisions but they should be rare enough to make the EventId a useful way to group errors.
One strategy would be to take the hashcode of the stacktrace but that would mean that the first and second calls in the following code would have generate the same event ID.
public void TestLog()
{
LogSomething("Moo");
// Do some stuff and then a 100 lines later..
LogSomething("Moo");
}
I thought of walking up the call stack using the StackFrame class which has a GetFileLineNumber method. The problem with this strategy is that it will only work when built with debug symbols on. I need it to work in production code too.
Does anyone have any ideas?

Here is some code you can use to generate an EventID with the properties I describe in my question:
public static int GenerateEventId()
{
StackTrace trace = new StackTrace();
StringBuilder builder = new StringBuilder();
builder.Append(Environment.StackTrace);
foreach (StackFrame frame in trace.GetFrames())
{
builder.Append(frame.GetILOffset());
builder.Append(",");
}
return builder.ToString().GetHashCode() & 0xFFFF;
}
The frame.GetILOffset() method call gives the position within that particular frame at the time of execution.
I concatenate these offsets with the entire stacktrace to give a unique string for the current position within the program.
Finally, since there are only 65536 unique event IDs I logical AND the hashcode against 0xFFFF to extract least significant 16-bits. This value then becomes the EventId.

The IL offset number is available without debug symbols. Combined with the stack information and hashed, I think that would do the trick.
Here's an article that, in part, covers retrieving the IL offset (for the purpose of logging it for an offline match to PDB files--different problem but I think it'll show you what you need):
http://timstall.dotnetdevelopersjournal.com/getting_file_and_line_numbers_without_deploying_the_pdb_file.htm

Create a hash using the ILOffset of the last but one stack frame instead of the line number (i.e. the stack frame of your TestLog method above).

*Important: This post focuses at solving the root cause of what it appears your problem is instead of providing a solution you specifically asked for. I realize this post is old, but felt it important to contribute. *
My team had a similar issue, and we changed the way we managed our logging which has reduced production support and bug patching times significantly. Pragmatically this works in most enterprise apps my team works on:
Prefix log messages with the "class name"."function name".
For true errors, output the captured Exception to the event logger.
Focus on having clear messages as part of the peer code review as opposed to event id's.
Use a unique event id for each function, just go top to bottom and key them.
when it becomes impractical to code each function a different event ID, each class should just just have a unique one (collisions be damned).
Utilize Event categories to reduce event id reliance when filtering the log
Of course it matters how big your apps are and how sensitive the data is. Most of ours are around 10k to 500k lines of code with minimally sensitive information. It may feel oversimplified, but from a KISS standpoint it pragmatically works.
That being said, using an abstract Event Log class to simplify the process makes it easy to utilize, although cleanup my be unpleasant. For Example:
MyClass.cs (using the wrapper)
class MyClass
{
// hardcoded, but should be from configuration vars
private string AppName = "MyApp";
private string AppVersion = "1.0.0.0";
private string ClassName = "MyClass";
private string LogName = "MyApp Log";
EventLogAdapter oEventLogAdapter;
EventLogEntryType oEventLogEntryType;
public MyClass(){
this.oEventLogAdapter = new EventLogAdapter(
this.AppName
, this.LogName
, this.AppName
, this.AppVersion
, this.ClassName
);
}
private bool MyFunction() {
bool result = false;
this.oEventLogAdapter.SetMethodInformation("MyFunction", 100);
try {
// do stuff
this.oEventLogAdapter.WriteEntry("Something important found out...", EventLogEntryType.Information);
} catch (Exception oException) {
this.oEventLogAdapter.WriteEntry("Error: " + oException.ToString(), EventLogEntryType.Error);
}
return result;
}
}
EventLogAdapter.cs
class EventLogAdapter
{
//vars
private string _EventProgram = "";
private string _EventSource = "";
private string _ProgramName = "";
private string _ProgramVersion = "";
private string _EventClass = "";
private string _EventMethod = "";
private int _EventCode = 1;
private bool _Initialized = false;
private System.Diagnostics.EventLog oEventLog = new EventLog();
// methods
public EventLogAdapter() { }
public EventLogAdapter(
string EventProgram
, string EventSource
, string ProgramName
, string ProgramVersion
, string EventClass
) {
this.SetEventProgram(EventProgram);
this.SetEventSource(EventSource);
this.SetProgramName(ProgramName);
this.SetProgramVersion(ProgramVersion);
this.SetEventClass(EventClass);
this.InitializeEventLog();
}
public void InitializeEventLog() {
try {
if(
!String.IsNullOrEmpty(this._EventSource)
&& !String.IsNullOrEmpty(this._EventProgram)
){
if (!System.Diagnostics.EventLog.SourceExists(this._EventSource)) {
System.Diagnostics.EventLog.CreateEventSource(
this._EventSource
, this._EventProgram
);
}
this.oEventLog.Source = this._EventSource;
this.oEventLog.Log = this._EventProgram;
this._Initialized = true;
}
} catch { }
}
public void WriteEntry(string Message, System.Diagnostics.EventLogEntryType EventEntryType) {
try {
string _message =
"[" + this._ProgramName + " " + this._ProgramVersion + "]"
+ "." + this._EventClass + "." + this._EventMethod + "():\n"
+ Message;
this.oEventLog.WriteEntry(
Message
, EventEntryType
, this._EventCode
);
} catch { }
}
public void SetMethodInformation(
string EventMethod
,int EventCode
) {
this.SetEventMethod(EventMethod);
this.SetEventCode(EventCode);
}
public string GetEventProgram() { return this._EventProgram; }
public string GetEventSource() { return this._EventSource; }
public string GetProgramName() { return this._ProgramName; }
public string GetProgramVersion() { return this._ProgramVersion; }
public string GetEventClass() { return this._EventClass; }
public string GetEventMethod() { return this._EventMethod; }
public int GetEventCode() { return this._EventCode; }
public void SetEventProgram(string EventProgram) { this._EventProgram = EventProgram; }
public void SetEventSource(string EventSource) { this._EventSource = EventSource; }
public void SetProgramName(string ProgramName) { this._ProgramName = ProgramName; }
public void SetProgramVersion(string ProgramVersion) { this._ProgramVersion = ProgramVersion; }
public void SetEventClass(string EventClass) { this._EventClass = EventClass; }
public void SetEventMethod(string EventMethod) { this._EventMethod = EventMethod; }
public void SetEventCode(int EventCode) { this._EventCode = EventCode; }
}

Thanks for the idea of hashing the call stack, I was going to ask that very same question of how to pick an eventId.
I recommend putting a static variable in LogSomething that increments each time it is called.

Now I want to use the EventId to try
and group related errors.
You have filters in event viewer so why (Go to find ? You have 65536 unique event IDs too.
Or rather use log4net or something ??
just my ideas....