I am beginner in c# with a huge problem.
An application with datagridview in front (Termin plan for one work day) works on many PC's in LAN with MS Windows Server and with MySQL database.
How can I become the changes made on one workstation AUTOMATICALY on all other PC's WITHOUT any action on them (application only started).
I have a procedure for data and datagridview refresh, I must only know WHEN I must start this procedure, that means I must know WHEN any other workstation made any changes.
Thanks for any help!
A simple solution would be to use a timer and when it elapses you refresh you gridview. so on defined period of time it will be refreshed automatically. the problem can be that if you update to often there's a overload of accessing the db. to prevent this, you could make an serverapplication which handles all data
Let's say PC 1 is starting the client application.
First it connects to server application (the server stores the reference of the client e.g. in an list).
After that the user on PC1 makes changes and click on save, the software will send the changes to the server (e.g. a custom object with all needed information).
Server saves the changes to the DB
Serverapplication give a response to the specific client if it worked or not
If it worked, Send an custom object (for example named ChangesDoneEvent) to all clients that indicates that changes have been done.
All connected clients will receive that object and know now that the have to refresh their gridview.
For further information just search for C# Multi threaded Server Socket programming. For sending custom objects over network you will find many resources in the internet too, maybe this will help you Sending and receiving custom objects using Tcpclient class in C#
Declare Delegate on your form
public delegate void autocheck();
private System.Timers.Timer TTTimer = new System.Timers.Timer();
public void autofilldgv()
{
if (this.InvokeRequired)
{
this.Invoke(new autocheck(UpdateControls));
}
else
{
UpdateControls();
}
}
private void UpdateControls()
{
//call your method here
filldgv();
}
void TTTimer_Elapsed(object sender System.Timers.ElapsedEventArgs e)
{
mymethod();
}
public void mymethod()
{
//this method is executed by the background worker
autofilldgv();
}
private void frm_receptionView_Load(object sender, EventArgs e)
{
this.TTTimer.Interval = 1000; //1 sec interval
this.TTTimer.Elapsed += new System.Timers.ElapsedEventHandler(TTTimer_Elapsed);
this.TTTimer.Start();
}
The solution provided above is actually a good way to handle this scenario. Before implementing you might also want to think about the potential fall backs. It is possible that Client PC 's IP could change and since you are using sockets. The object reference added in the list could be faulted state. You might want to think of handling this pitfall.
Related
Good evening,
In my SignalR application I have a javascript timer that is ran for all users "simultaneously". At the end of this timer, a server function is called, and this is where this problem starts.
As the function is called at the end of the timer, every connected user calls it at the same time, which is unnecessary because it will return the same output for all connected users. Being a logically complex function, having the server run it unnecessarily for all users adds up to be a great resource waste.
How can I make it so that it is ran only once (maybe the first time it is called (until the next timer stops))?
Thank you in advance
You could make use of GlobalHost.ConnectionManager.GetHubContext. This will allow you to get any hub context and then trigger Clients.All.YourFunction on that context. That will send send a message to all connected clients subscribed to that hub.
You will need to have a background process that runs every at the time your JavaScript function fires (by the way, relying on all your clients to call a JavaScript function simultaneously is really not a good idea; different client locations and different machine performance will mean they're not likely to be simultaneous).
The following is assuming that you're just running this on a single server. If you're going to be deploying this to a web farm, then you'll need to use a Database value to ensure you don't repeat the same work, or set up a particular server instance to be responsible for doing the calls (otherwise you'll end up with one call per server).
Create a process that runs in the Background (I'm sticking with a simple thread here, I actually use HangFire for this, but this will suffice for the example), e.g. On App_Start
Thread thread = new Thread(new ThreadStart(YourFunction));
thread.Start();
Then create YourFunction which will be responsible for your client calls:
private bool Cancel = false;
private void YourFunction()
{
do
{
string foo = "Foo";
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<YourHub>();
context.Clients.All.SendYourMessage(foo);
Thread.Sleep(10000);
}
while(!Cancel)
}
And then on the client, just handle the message from the hub:
youyHub.client.sendYourMessage = function(message)
{
// message == "Foo"
};
I need to write code in C# that sends data from Serial to an Arduino every 2 seconds.
This is what I tried to do:
Thread sender = new Thread(voidSender);
public static void voidSender() {
serialArduino.WriteLine("Test");
Thread.Sleep(2000);
}
In your example you are starting a thread running through the defined method, sending a single message. To send the message multiple times you need to add a loop to this method like
public void voidSender()
{
//Send forever
while(true)
{
serialArduino.WriteLine("Test");
Thread.Sleep(2000);
}
}
However, periodically events are typically done by using a timer. Simply initialize a timer like
System.Timers.Timer sendMessageTimer = new System.Timers.Timer(2000);
sendMessageTimer.Elapsed += OnSend;
sendMessageTimer.AutoReset = true;
sendMessageTimer.Enabled = true;
Inside the elapsed handler you can send the message like
private void OnSend(Object source, ElapsedEventArgs e)
{
serialArduino.WriteLine("Test");
}
Honestly I don't why you would mix open source platform such as Arduino with C# .net if its not running on core, but that's your concern not mine, I personally wouldn't do that.
if you want to send command every two seconds, I would advise you to use windows scheduler that's integrated in every windows system, however you can implement a clock on your own very easy, still why would you need to put such heavy load of 2 seconds timeframe when it will be almost notable by ordinary user. If you don't want to use clock based system you can use this modified example however it may throw stackoverflow exception sometime since its recursion and you must aways stay away from them if you plan to use this on the long run.
//First sorry for reusing your code but I am writing from my smartphone and
//I am kind of lazy here is quick modification that would work but not the most clever way around
Thread sender = new Thread(voidSender);
public static void voidSender()
{
start:
serialArduino.WriteLine("Test");
Thread.Sleep(2000);
goto start;
}
I simply want to be able to make a callback on a function in the windows phone code from the server side when something is being updated there. Examples abound on the Internet make use of wsDualHttpBinding, but some wise man has decided to remove support for that from the windows store application API list. I can't find any other way to get the same functionality, does anybody know how to do this?
The reasoning behind not allowing for internet based callbacks is that it puts a big drain on the phone's battery to be constantly listening for them. Instead, they allow you to run PeriodicTask's that will let you occasionally call a server to poll whether there is a change.
Alternatively you could use their notification service:
http://msdn.microsoft.com/en-us/library/windowsphone/develop/ff402558%28v=vs.105%29.aspx
You can try something like this
System.Net.WebClient wc = new System.Net.WebClient();
public void Initialize(object sender, EventArgs e)
{
wc.DownloadStringCompleted += new System.Net.DownloadStringCompletedEventHandler(done);
}
public string version = "1.0.0";
public void done(object sender, System.Net.DownloadStringCompletedEventArgs e)
{
if (version != e.Result)
{
//Do your code here
}
}
You can create a place online that stores the current version then check on start up.
I hope I can get some help.
I’m trying to create an host based application using C# (in the simplest way) to monitor access to a web page from the computer that hosts the application, if this web page is accessed while the program is running an event should rise.
So far I have used the SHDocVw.ShellWindows() but it works only if the web page has already been accessed not while is being accessed.
It monitors Windows Internet Explorer
I have also researched the httplistener but to no avail.
Do you have any solution?
Please let me know if you require more details
This may or may not be valid for your situation, but I had to do something similar with an Intranet website (cross-browser so it was a little harder than just with IE) recently. My solution was to setup a client-side application which hosts a WCF service. Then, when the user clicks a link on the web page (or raises any event, such as, $(document).ready) it sends an message back to the server telling the server to connect to the IP address associated with the current session (really just the IP Address on the request) on a known port. This connection is made to the client side application which is listening at that IP address and port for instructions on what to do (in my case it is dynamically compiling code in the request and running it).
That of course will only work for Intranet websites. A more general approach that will work for IE across the internet, is to create a IE extension (or maybe a Silverlight application) that talks on localhost. I've never done it, so I can't tell you how or if it is actually possible (but in principle seems possible).
If you don't have access to the website at all then perhaps using SharpPCAP or the Fiddler API would work for you.
Assuming the question is "I want to know when a program on my local computer accesses a give web page": A transparent http proxy is likely approach you want to take. Check out Fiddler to see if it is exactly what you want.
If your question is more "I want to know when a particular page is hit on my remote server": There are plenty of monitoring tools that parse web server logs and event logs to know state of the server. If you want to do something yourself and control the server's code - collect hit information for the page you are interested and provide some page that reports this data.
After few hours of work I have found a solution, not the most elegant one so far,(and at times causes a memory dump) but it does what I need.
Thanks
Just last edit, I solved the crash issue by adding a time so it checks the page every sec or so.
once again thanks for your iterest in my question.
class wait
{
private static System.Timers.Timer aTimer;
public void timed1()
{
// Create a timer with a ten second interval.
aTimer = new System.Timers.Timer(10000);
// Hook up the Elapsed event for the timer.
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
// Set the Interval to 2 seconds (2000 milliseconds).
aTimer.Interval = 2000;
aTimer.Enabled = true;
Console.WriteLine("Press the Enter key to exit the program.");
Console.ReadLine();
}
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
//NetKeyLogger klog = new NetKeyLogger();
// Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
Kelloggs.Program KKA = new Kelloggs.Program();
SHDocVw.ShellWindows shellWindows = new SHDocVw.ShellWindows();
string filename;
foreach (SHDocVw.InternetExplorer ie in shellWindows)
{
filename = Path.GetFileNameWithoutExtension(ie.FullName).ToLower();
if (filename.Equals("iexplore"))
{
string ddd = (ie.LocationURL);
// Console.WriteLine(ddd);
if (ie.LocationURL == "http://www.testPage.com/")
{
Console.WriteLine("Page found");
// Console.ReadLine();
aTimer.Enabled = false;
KKA.Maino();
}
}
In my C# Windows Forms application , I retrieve some data from WebServices over the Internet. Refresh every second
It works as asynchronous operations and works well but whenever application gets disconnected from Internet, it shows an exception, and when it reconnects to the Internet, program should work automatically and immediately.
Currently, the program takes more then one minute to start working again, and I would like the exception to be ignored when connection drops.
it refreshed every second , it mean there are plenty of threads running at same time and
when they all done , then it comes to connecting
What solution i can use so my programs runs ASAP when internet connects?
public void loadbalance()
{
try { //Get Data from Internet }
catch { }
}
delegate void loadbalancedelegate();
public void loadBalanceAsync()
{
loadbalancedelegate worker = new loadbalancedelegate(loadbalance);
AsyncCallback LoadbalnceCallBack = new AsyncCallback(loadbalanceCompleted);
AsyncOperation async = AsyncOperationManager.CreateOperation(null);
worker.BeginInvoke(LoadbalnceCallBack,async);
}
public void loadbalanceCompleted(IAsyncResult result)
{
loadbalancedelegate worker = (loadbalancedelegate) ((AsyncResult)result).AsyncDelegate;
AsyncOperation async = (AsyncOperation)result.AsyncState;
worker.EndInvoke(result);
}
delegate void setControlsBalanceDelegate(BalanceOB ball);
void setControlsBalance(BalanceOB ball)
{
if (this.InvokeRequired)
this.Invoke(new setControlsBalanceDelegate(this.setControlsBalance), new
object[] { ball });
else
{ //Update Data on Form (Windows App)
}
}
I would probably do the following:
In your timer code which runs every second, I would check if the internet connectivity is available by P/Invoke (which is faster way than having the service throw an exception, and looks like it would suit your cause as well). For some reference look here
I would have the P/invoke code also set a flag temporarily somewhere (make sure it is thread safe) and before making any web service calls, i would check if the flag is in a valid state for the client to make that call.