Threading and cross-threading - C# Discussion Boards

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 />

#region signature
my articles
#endregion

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

c0ax_lx2-Nov-07 3:00

c0ax_lx

2-Nov-07 3:00

That would not work, consider

<br />
 TreeNode tn1 = new TreeNode("item1");<br />
 TreeNode tn2 = new TreeNode("item1");<br />
 treeView1.Nodes.Add(tn1);<br />
 if(!treeView1.Nodes.Contains(tn2)){<br />
     treeView1.Nodes.Add(tn2);<br />
  }else{<br />
    // dont add node<br />
  }<br />

treenode tn2 has the text as tn1, but it is not THE same treenode.
but you could use the Name property and ContainsKey method

<br />
 TreeNode tn1 = new TreeNode("item1");<br />
            tn1.Name = "item1";<br />
<br />
            TreeNode tn2 = new TreeNode("item1");<br />
            tn2.Name ="item1";<br />
            treeView1.Nodes.Add(tn1);<br />
        <br />
            if(!treeView1.Nodes.ContainsKey(tn2.Name )){<br />
                treeView1.Nodes.Add(tn2);<br />
            }else{<br />
                MessageBox.Show("node exists"); <br />
            }<br />
<br />

If it' stuck, DO NOT pull harder!

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

Kenth Ringsby2-Nov-07 9:57

Kenth Ringsby

2-Nov-07 9:57

Thanks.

The last example was just the one I was looking for. It works great !

Big Grin | :-D

KRR

String.Format question

Seraph_summer2-Nov-07 2:18

Seraph_summer

2-Nov-07 2:18

Is it possible to use two or more kinds of format for String.Format()?
For example, If I want to display the 1.452677e-12 as 1.45e-12, how to do?

thanks

Re: String.Format question

snorkie2-Nov-07 4:57

snorkie

2-Nov-07 4:57

Sure, why not... There are many ways to do that.

simplest way...
string result = String.Format();
result = String.Format();

depending on the formatting you are doing, you could also do
.ToString().ToString() and use the standard IFormatProviders.

Hogan

How to convert mm/dd/yy to dd/mm/yy

Arif patel2-Nov-07 1:47

Arif patel

2-Nov-07 1:47

Hi,
can Any one tell me how to convert mm/dd/yy to dd/mm/yy format.....

Arif patel

Re: How to convert mm/dd/yy to dd/mm/yy

Pete O'Hanlon2-Nov-07 1:52

Pete O'Hanlon

2-Nov-07 1:52

Arif patel wrote:
can Any one tell me how to convert mm/dd/yy to dd/mm/yy format.....

Sure, use .ToString("dd/mm/yy");.

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

Re: How to convert mm/dd/yy to dd/mm/yy

Arif patel2-Nov-07 2:06

Arif patel

2-Nov-07 2:06

Hi pete,

I have wrote like this

Label2.Text=DateTime.Now.ToString("dd/mm/yy");

But i am getting like this 02/27/07 which is wrong...plz reply me..

Arif patel

Re: How to convert mm/dd/yy to dd/mm/yy

Pete O'Hanlon2-Nov-07 2:09

Pete O'Hanlon

2-Nov-07 2:09

Sorry - The mm should be MM. So this would be Label2.Text=DateTime.Now.ToString("dd/MM/yy");

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

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