Re: Accessing control from seperate class - C# Discussion Boards

Pete O'Hanlon2-Nov-07 10:59

2-Nov-07 10:59

waheed awan wrote:
i didnt understand the advantage of using delegates i want to know some practical aspect why to use delegates?

Well, if you have to attend a conference and don't want to take time away from the bar to go to talks, you could hire somebody to go for you - they would be your delegates.

Deja View - the feeling that you've seen this post before.

Re: Delegates

sabrown1002-Nov-07 13:45

sabrown100

2-Nov-07 13:45

But what's the point in coding?

Re: Delegates - Productive [modified]

KennyPatel2-Nov-07 22:35

KennyPatel

2-Nov-07 22:35

Hi. I hope you Will find your answer in this link.

http://www.exforsys.com/tutorials/csharp/delegates-in-csharp.html[^]

Thanks

-- modified at 4:42 Saturday 3rd November, 2007

Thanks

Frame refresh information

Yigal Agam2-Nov-07 5:26

Yigal Agam

2-Nov-07 5:26

Hi,

Does anyone know if it's possible to trigger an event whenever a video frame is being refreshed (e.g., every 50 ms for a 20 fps frame rate)? It can be either with DirectX or WMP SDK.

Thank you,
Yigal Agam

Read web.config authorization's

GreenGiant832-Nov-07 4:53

GreenGiant83

2-Nov-07 4:53

My site is using Windows Authentication. I have an Admin folder setup with a web.config to restrict access to all but a few specific people. Like this

<authorization>
  <allow users="ab123"/>
  <allow users="xy789"/>
  <allow users="op456"/>
  <deny users="*"/>
</authorization>

In my code for a page that does not reside in that protected directory I want to detirmine if a user has access to that folder. Is anyone aware of a method to do this?

Matt

Accessing control from seperate class

oceanexplorer2-Nov-07 4:10

oceanexplorer

2-Nov-07 4:10

Hi,

I need to call an invoke method on a list box called lstLogger, e.g.

lstLogger.BeginInvoke(delegate, object)

However that would be fine if I was in the same class as the lstLogger, but I'm in a seperate class. How can I access lstLogger in order to call the BeginInvoke method?

Regards

Paul

Re: Accessing control from seperate class

led mike2-Nov-07 4:59

led mike

2-Nov-07 4:59

Paul, I hate to say this but your question makes you sound like this is your first day programming. How you access object A from object B is that object B must have a reference to object A. Now there are many, many ways for this to happen so I don't know what you want us to tell you.

Re: Accessing control from seperate class

oceanexplorer2-Nov-07 5:11

oceanexplorer

2-Nov-07 5:11

Yep I know I'm having a dumb blonde moment!

To be honest I know about accesing controls from other classes etc. But my difficulty with this one is I am dealing with threading, I have a UI that runs on one thread, when a button is pressed, it creates a new thread and goes of and executes another (labour intensive task), within the running task I want to make callbacks to the UI to update a listbox with messages.

I have setup the delegates fine but my trouble is in accessing the listbox control to call the begininvoke method e.g.

lstLogger.BeginInvoke(delegate, object)

To call this from the other class I would need to create a new instance of the Logger class which contains the listbox lstLogger, but I don't want to do this, I want to invoke a method on a seperate thread that is already running.

It's driving me nuts, all the examples I can find do it from within the same class, which is easy to set up as I have access to the lstLogger control.

Hope that explains a bit more and doens't make me sound so dumb!

Regards

Paul

Re: Accessing control from seperate class

led mike2-Nov-07 5:22

led mike

2-Nov-07 5:22

oceanexplorer wrote:
But my difficulty with this one is I am dealing with threading

Slow down and relax. The threading issue is completely separate from the object access issue. You actually seem to be aware of that but perhaps your frustration is not allowing you to realize it.

oceanexplorer wrote:
To be honest I know about accesing controls from other classes etc.

Then start there. Don't think about the thread issue and solve the access problem first. Once you have access to the object then go back to solving the thread issue.

#1 Get access to the object I need.
#2 Now I am in another thread so I need to Invoke the object rather than just call it's method.

Also take a look at this[^] and see if it helps.

Re: Accessing control from seperate class

oceanexplorer2-Nov-07 5:35

oceanexplorer

2-Nov-07 5:35

Thanks Mike,

It's friday, I'm bored of thinking and want to go home!!

In order to gain access to the object, I tired making it public rather than private but I still cannot see it, public static allows me to see it but then that causes hassle in construction and it won't build.

I would normally create public property accessors but I need access to the object in order to invoke methods.

Any ideas?

Thanks again

Paul

Re: Accessing control from seperate class

led mike2-Nov-07 7:09

led mike

2-Nov-07 7:09

oceanexplorer wrote:
It's friday, I'm bored of thinking and want to go home!!

oceanexplorer wrote:
Any ideas?

Sounds like you need to go home and come back to this with a fresh mind on Monday. If you put any efforts in over the weekend I would suggest limiting that to reading some design material, perhaps patterns or something. Nothing directly related to your project.

C# based web service: Referring IP address?

Jerry Evans2-Nov-07 4:03

Jerry Evans

2-Nov-07 4:03

Does anyone know how to get to the HTTP headers when executing a web service method? Specifically I'm interested in checking the IP Address of the client requesting a web page (REMOTE_ADDR).

Thanks

Jerry

Re: C# based web service: Referring IP address?

Jerry Evans2-Nov-07 4:53

Jerry Evans

2-Nov-07 4:53

Found it thanks. For the record:

string uha = Context.Request.UserHostAddress.ToString();

Execute script with trasaction on firebird database server

Razvan Dimescu2-Nov-07 3:41

Razvan Dimescu

2-Nov-07 3:41

Hello,

I'm trying to execute a script from a file and I noticed I can only do it using a FbBatchExecution. The problem is I can't find how to add a transaction to the batch execution. Can i use the FbBatchExecution with a command and specify a transaction to that command? Can you please point me in some directions? I'm confused Sigh | :sigh:

Thank you!

drinking beer is fun Smile | :)

Re: Execute script with trasaction on firebird database server

Razvan Dimescu2-Nov-07 4:46

Razvan Dimescu

2-Nov-07 4:46

Ok inseatd of adding sql statements to a FbBatchExecution I just executed each statement using a command it looks ugly, but it works Smile | :)

                <br />
foreach (string cmd in script.Results)<br />
                {<br />
                    fbCommand.CommandText = cmd;<br />
                    fbCommand.ExecuteNonQuery();<br />
                 }<br />

drinking beer is fun Smile | :)

Threading and cross-threading

oceanexplorer2-Nov-07 3:16

oceanexplorer

2-Nov-07 3:16

Hi,

I have created a windows form the contains a button and a list box. When the button is clicked it fires the following code,

 <br />
Migration.Begin();<br />
thread = new Thread(new ThreadStart(Migration.Begin));<br />
thread.Start();<br />

Migration is a seperate class that is executed on a new thread as it will be a labour intensive task and I want the UI to remain usable.

However within the migration module I want to be able to call back to the thread that created the UI and have it append a message to the listbox.

So intially in the UI class I added a delgate which called a seperate function to add a line to the listbox:

<br />
public static LoggerListDelegate loggerListDelegate;       <br />
        <br />
public Logger()<br />
{<br />
    InitializeComponent();<br />
    loggerListDelegate = new LoggerListDelegate(AddLine);<br />
}<br />

And the function addline was as follows:

<br />
public void AddLine(string line)<br />
{<br />
    lstLogger.Items.Add(DateTime.Now.ToLongTimeString() + ": " + line);           <br />
}<br />

I then called this from the Migration using the following:

<br />
Logger.loggerListDelegate.BeginInvoke("******Migration has begun******",null,null);<br />

This however is giving me an issue that it is not thread safe as I am trying to invoke on different thread the list was created on.

So my understanding is that I would really need to call the Listbox invoke method, e.g.

lstLogger.Invoke(delegate, objects)

If that's correct how do I access the lstLogger from my Migration class in order to invoke it?

If this is not right how do I go about making it threadsafe?

Many many many thanks

Paul

Re: Threading and cross-threading

Daniel Grunwald2-Nov-07 3:29

Daniel Grunwald

2-Nov-07 3:29

There is a huge difference between Control.BeginInvoke and Delegate.BeginInvoke: Delegate.BeginInvoke will call the method on a thread from the ThreadPool, but Control.BeginInvoke will call the method on the thread that runs the message loop for that control (which usually is the main thread). Since the main thread created the form and the controls on it, it is the only thread allowed to access the controls. So you have to use Control.BeginInvoke (lstLogger.BeginInvoke or this.BeginInvoke if "this" is a form).

Re: Threading and cross-threading

oceanexplorer2-Nov-07 3:37

oceanexplorer

2-Nov-07 3:37

Hey Daniel,

thanks for a great response, that makes it a lot clearer for me, I was having major mental block!

I have just one further question, what is the best way for me to access the lstLogger control from a seperate class? I tried changing the control to public static but the obviously is incorrect.

I could in the migration class create a new instance of the Logger class and call it-

Logger log = new Logger();
log.lstLogger.BeginInvoke(delegate, objects)

But that won't work properly, what are you thoughts?

Thanks again

Paul

Can anyone still answer this?

oceanexplorer2-Nov-07 5:13

oceanexplorer

2-Nov-07 5:13

Can anyone still answer this?

Re: Threading and cross-threading

m@u2-Nov-07 6:29

m@u

2-Nov-07 6:29

Hi
I would do the following:

let's say you have 2 classes the worker class Worker and the Main Form frmMain

public class Worker
{
    public event EventHandler MyInterThreadEvent;
    public Worker()
    {
        // do something here
    }
    protected virtual void onMyInterThreadEvent(EventArgs e)
    {
        if (MyInterThreadEvent != null)
        {
            MyInterThreadEvent(this, e);
        }
    }
    public void ThreadMethod()
    {
         do
         {
            // do something here
            onMyInterThreadEvent(EventArgs.Empty);
         }while(something);
    }
}
public class frmMain:Form
{
    private Worker MyPersonalSlave;
    // .. All the Form - Stuff coming here...
    public frmMain()
    {
        InitializeComponent();
        MyPersonalSlave = new Worker();
        MyPersonalSlave.MyInterThreadEvent += new EventHandler(MyPersonalSlave_MyInterThreadEvent);
        // start a thread here that makes you worker work.
    }
    private void MyPersonalSlave_MyInterThreadEvent(object sender, EventArgs e)
    {
        if (!InvokeRequired) // are we in the correct Thread?
        {
            // do what ever you want to do when the event gets fired
        }
        else // use the invoke on the form to run this method in the correct Thread
        {
            Invoke(new EventHandler(MyPersonalSlave_MyInterThreadEvent),new object[]{sender,e});
        }
    }
}

Greets
m@u

XP ICONS

half-life2-Nov-07 2:41

half-life

2-Nov-07 2:41

HI,

l like to know how can i use the xp icons
from where do i get them

THANKS

Smile | :)

Have Fun
Never forget it

Re: XP ICONS

Pete O'Hanlon2-Nov-07 3:31

Pete O'Hanlon

2-Nov-07 3:31

You can get the Microsoft Common Icons here[^].

Deja View - the feeling that you've seen this post before.

Re: XP ICONS [modified]

half-life2-Nov-07 5:00

half-life

2-Nov-07 5:00

THANKS

but is'nt there a way to get out of the the system (XP)?

i cant find them with SEARCH

-- modified at 11:11 Friday 2nd November, 2007

Like getting out of shell32.dll???

Have Fun
Never forget it

How can I check if a node in a treeview allready exist ?

Kenth Ringsby2-Nov-07 2:31

Kenth Ringsby

2-Nov-07 2:31

I have a treeview where I add nodes. Before I add a new node to the treeview I want to check if a node with the same name allready exist, how can I do that in an easy way ?

KRR

Re: How can I check if a node in a treeview allready exist ?

Giorgi Dalakishvili2-Nov-07 2:53

Giorgi Dalakishvili

2-Nov-07 2:53

<br />
if (!treeview1.Nodes.Contains(nodetoadd))<br />
{<br />
//treeview1 doesn't contain nodetoadd<br />
}<br />
else<br />
{<br />
//treeview1 contains node nodetoadd<br />
}<br />

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