How Do I Return A Value After Displaying A Windows Form.

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Good day Coders, kindly help me resolve a logical error within my code. I'm initializing a form from one class and then call a method inside the form to display it and then return a boolean value, to the calling method in the class. My problem is, once the form is displayed, the focus is not going back to the method awaiting the boolean value to be returned. Below is a sample code:

C#

class MessageProcessor
{
    string responseMsg = string.Empty;
    
    public void isFormDispalyed()
    {
        ItemMonitor itemMonitor = new ItemMonitor (); //Form initialization
        
        IntPtr handle = itemMonitor .Handle;
        
        if (itemMonitor.RemoteMonitor())
        {
            responseMsg =  "Surveillance Initiated";
        }
        else
        {
            responseMsg = "Surveillance Couldnt Be Started";
        }   
    }
}


public partial class ItemMonitor : Form
{
    public bool RemoteMonitor()
    {
        this.Invoke(new ClearOutPutBoxEvent(ClearOutPutBox));
        
        isStartButtonClicked = true;
        
        object isOpen = null;
        
        isOpen = this.Invoke(new RemoteScanEvent(ComPortSetup));
        
        this.Invoke(new Action(() = this.ShowDialog()));//pragram never proceeds until the form is closed.
        
        return Convert.ToBoolean(isOpen);//Must return this value to the calling method
    } 
}

Posted 17-Sep-14 11:22am

Admire Mhlaba

Updated 17-Sep-14 16:00pm

George Jonsson

v2

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Comments

Sergey Alexandrovich Kryukov 17-Sep-14 18:05pm

Unfortunately, the question, as formulated, does not seem to make any sense. The term "focus" is related exclusively to certain UI. At a time, there is on control in the whole desktop, which holds keyboard focus and responds to major input from the keyboard (not counting hot keys, keyboard accelerators, hooks, etc.). The focus cannot "go back to method", because this notion is not applicable to methods. Even though there could be some real problem behind your post (or not real :-), you did not explain it. The code sample also does not help much to see the problem, because nearly nothing tells us how different point in this code are related to your textual description. RemoteMonitor returns bool (why?), what what?..
—SA

Admire Mhlaba 18-Sep-14 2:21am

Thank you for your kind response, well RemoteScanEvent invokes ComPortSetup Method that returns a boolean value to denote a success or failure and that is the value I'm trying to return back such that some other events can be triggered based on that.

Sergey Alexandrovich Kryukov 18-Sep-14 2:44am

First, modal ShowDialog won't return before you close it. There is nothing you can do it. If it does not work for you, change the UI design. If this method called from some other, not UI thread? (In not, you don't need this.Invoke. And why not Invoking the whole call to this method?)
—SA

Admire Mhlaba 18-Sep-14 2:50am

Thank you for your kind input,i will consider your suggestion. Just a quick note, if I use this.Show() it does return the focus back but the form becomes unresponsive or hangs? Any idea how to allay this.

Sergey Alexandrovich Kryukov 18-Sep-14 2:55am

You really should learn using threads with UI. This is the key. Well, could you show the code with Show()? Could you explain your goals in sufficient detail.
—SA

Admire Mhlaba 18-Sep-14 3:03am

I have class that receives sms messages, I then call a specific form based on the message sent to the system. I'm using Ozeki as my gateway. Currently I have a rfid scanner attached to my com port so RemoteMonitor method starts up the serail communication with rfid hard and displays rifd tag readings on the form. If the serial port is opened then I must send back the boolean value and use it to inform the sms sender if the system is running or not.

BillWoodruff 17-Sep-14 22:35pm

Control doesn't return to the instance of 'MessageProcessor because you use 'ShowDialog to show the second Form, and thus flow-of-control passes to the thread the second Form is on until it is closed.

So, why are you using 'ShowDialog ?

Admire Mhlaba 18-Sep-14 2:23am

Good day, thank you for your response, I'm using showDialog to display ItemMonitor form such that I can see data being generated by hardware connected to com ports

BillWoodruff 18-Sep-14 3:05am

The question is: is it absolutely necessary to use 'ShowDialog ? Why are you making that choice ?

Also, when you say: "if I use this.Show() it does return the focus back but the form becomes unresponsive or hangs?" can you be more specific about this ?

Is it the case that you create multiple instances of the class 'MessageProcessor, and multiple instances of the ItemMonitor Form ?

good luck, Bill

Admire Mhlaba 18-Sep-14 3:13am

Hi, no I'm not creating multiple instances or either instances, I think the form is unable to continue running on the current thread.

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BillWoodruff · Answer 1 · 2014-09-17T21:12:00

Even though I do not fully understand your code choices yet, I'm going to post an "idea" here; if this would not work for you, perhaps if you explain why it would not work, we'll have a better understanding of what you are trying to do.

I assume that if the call to 'RemoteMonitor returns 'false that you will not want to show the 'itemMonitor Form instance:

C#

public class MessageProcessor
 {
     private string responseMsg = string.Empty;

     private ItemMonitor itemMonitor = new ItemMonitor(); //Form initialization

     public void isFormDispalyed()
     {
         if (itemMonitor.RemoteMonitor())
         {
                responseMsg = "Surveillance Initiated";
                
                // edit #2:
                
                // these settings should be set at design-time for the Form
                // they are shown here for educational purposes only
                itemMonitor.ShowInTaskbar = false;
                itemMonitor.TopMost = true;
                
                // this must be set in code
                itemMonitor.TopLevel = true;
                
                itemMonitor.Show();
                
                // handle sending SMS messages here ?
         }
         else
         {
                // edit #1: close the instance of the 'ItemMonitor: probably unnecessary
                // see: http://stackoverflow.com/questions/3097364/c-sharp-form-close-vs-form-dispose
                // for why 'Close is used here
                itemMonitor.Close();
                
                responseMsg = "Surveillance Couldnt Be Started";
         }
     }
 }

 public partial class ItemMonitor : Form
 {
     public bool RemoteMonitor()
     {
         this.Invoke(new ClearOutPutBoxEvent(ClearOutPutBox));

         isStartButtonClicked = true;

         object isOpen = true;

         isOpen = this.Invoke(new RemoteScanEvent(ComPortSetup));

         return Convert.ToBoolean(isOpen); //Must return this value to the calling method
     }
 }

Admire Mhlaba · Answer 2 · 2014-09-18T02:24:00

Solution 2

I have listened your informative suggestion and decided to change the way the form is accessed. The problem has been laid to rest now. Thank you all for your kind help and time.

Posted 18-Sep-14 2:24am