Question

out of order execution due to event function

Asked by: NewtonianB

I developed a small example to demonstrate my problem. execute() triggers a perl script that then returns output to myProcess_OutputDatReceived which updates a local variable.
The problem i'm having is that execute2() starts executing before value has been set. How do I fix this?

public class myClass
{
    public string value;
 
    public main()
    {
        execute();
        execute2();
    }
	public void execute()
    {
            Process myProcess = null;
            myProcess = new Process();
 
            ProcessStartInfo myProcessStartInfo = new ProcessStartInfo("perl.exe");
            myProcessStartInfo.Arguments = "blabla.pl"
            myProcess.OutputDataReceived += new DataReceivedEventHandler(myProcess_OutputDataReceived);
            myProcess.Start();
            myProcess.WaitForExit();
            myProcess.BeginOutputReadLine();
    }
    public void myProcess_OutputDataReceived(object sender, DataReceivedEventArgs e)
    {
        value = "test";
    }
 
	public void execute2()
    {
        // value is unassigned
    }
}

                                  
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Asked On
2009-09-15 at 13:15:29ID24734314
Topics

.NET

,

C# Programming Language

Participating Experts
1
Points
500
Comments
12

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Answers

 

by: p_davisPosted on 2009-09-15 at 13:27:54ID: 25339036

what about calling execute2 when the value is assigned in the event of the output being received?

 

by: p_davisPosted on 2009-09-15 at 13:29:45ID: 25339052

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public class myClass
{
    public string value;
 
    public main()
    {
        execute();
     
    }
        public void execute()
    {
            Process myProcess = null;
            myProcess = new Process();
 
            ProcessStartInfo myProcessStartInfo = new ProcessStartInfo("perl.exe");
            myProcessStartInfo.Arguments = "blabla.pl"
            myProcess.OutputDataReceived += new DataReceivedEventHandler(myProcess_OutputDataReceived);
            myProcess.Start();
            myProcess.WaitForExit();
            myProcess.BeginOutputReadLine();
    }
    public void myProcess_OutputDataReceived(object sender, DataReceivedEventArgs e)
    {
        value = "test";

             execute2();
    }
 
        public void execute2()
    {
        // value is unassigned
    }
}

 

by: NewtonianBPosted on 2009-09-15 at 13:31:30ID: 25339083

well that's actually the way I have it now but I wanted to keep it all calls organised in main.

 

by: NewtonianBPosted on 2009-09-15 at 13:32:22ID: 25339099

and thats for exception handling on top of just organization reasons

 

by: p_davisPosted on 2009-09-15 at 13:34:57ID: 25339144

what benefit are you trying to accomplish by doing that?

you would have to put in some kind of wait or while loop and that would be bad.

 

by: p_davisPosted on 2009-09-15 at 13:35:26ID: 25339150

sorry i was formulating my response when you wrote 25339099

 

by: p_davisPosted on 2009-09-15 at 13:36:36ID: 25339170

whatever you can do in main you can do elsewhere. as long as you have logical flow it would still be considered organized.

 

by: p_davisPosted on 2009-09-15 at 13:40:53ID: 25339228

i see from another question that you are concerned about error notification -- you could always create an event that the other pages can subscribe to as method to pass errors.

 

by: NewtonianBPosted on 2009-09-15 at 13:59:02ID: 25339437

ok let me try to be clearer so you can understand my problem.
From Page_Load I have access to elements on the .aspx page, essentially the html the user will see.
Now i am actually analyzing the output from my depending on results, I want the output to be displayed on the html page. My problem is right now I have no way of doing that because my main function finishes executing before this one...

 

by: NewtonianBPosted on 2009-09-15 at 13:59:32ID: 25339445

p_davis your last suggestion sounds like it could go somewhere, do you have anymore information on this?

 

by: p_davisPosted on 2009-09-15 at 14:00:48ID: 25339458

heading home will discuss more later

unless you are willing to use msdn and research adding your own events. -- not difficult just confusing at first.

 

by: p_davisPosted on 2009-09-16 at 05:32:56ID: 25344857

public event EventHandler SomethingFailed;//event


//when you want to notify the objects that are waiting for an event to happen
if(SomethingFailed != null)
             SomethingFailed.Invoke(this, new EventArgs());


//this is a basic event that  invokes a void type method. you can set this up for any return type and any argument parameters you want.

20120131-EE-VQP-002

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