I am new to this forum and this is my first post.

I am working on a C# project. General outline of the project is:

FORM 1 collects data as entered by the user (in text boxes, radio buttons, check boxes, numeric up-down controls etc) .

FORM 1 then does some calculations using this data and prepares a text message. I have a class created to do this job and updated Message is with the Class.

FORM 2 should take this text message and display it using a Rich text box.

User typically opens FORM 2 as and when it is needed to see the Message. User can kill/minimize FORM 2 . There is a button on FORM 1 to show FORM 2.

FORM 1 must update the FORM 2 whenever a new Message is generated provided FORM 2 is already instanced ( either showing or in minimized state.)

When FORM 2 is instanced by FORM 1 it must get the message from Form 1, so that upon instancing the FORM 2 shows the latest message from FORM 1.

I have coded something which worked , but I am a bit skeptical about the approach. Please guide me.

What I am doing is:

FORM 2 which displays the Message string, is instanced as:

public string messageIn;

public FORM2(string myMessage)
	messageIn = myMessaage; // input string to on FORM public variable

In FORM 2 I have a public method:

public  void ShowMessage(messageIn)

I call this ShowMessage in the form_load method:

private void FORM2_Load(object sender, EventArgs e)

In FORM 1 , have to call this ShowMessage in FORM 2 so that update message gets displayed on FORM 2.

There are two possibilities:

1> FORM 2 is not yet instanced : I shouldn't care to update it.
2> FORM 2 is already instanced.I must update FORM 2

So check that part first as:

bool IsOpen = false;
            foreach (Form f in Application.OpenForms)
                if (f.Text == "FORM2")
                    IsOpen = true;  // FORM found
            } // Loop to check next FORM
			// If FORM2 is already instanced then and then only update 
			// If FORM2 is not instanced , no need to update
            if (IsOpen == true) 
				// FORM2 already instanced , OK to update it
                FORM2 f1 = (FORM2)Application.OpenForms["FORM2"];


When user Clicks on the button on FORM 1 to view message, I check first the whether the form is already instance or not.
If it is there already, I call the the method in FORM 2 as shown above, else I instance the FORM 2 as:

FORM2 frm2 = new FORM2(message);// message goes as FORM2 constructor input argument

I am a bit worried about using:

FORM2 f1 = (FORM2)Application.OpenForms["FORM2"];

Is it safe (legitimate)/ good practice or it might pose some potential problems later?

Or is there any better / clean way of doing this?



Recommended Answers

All 3 Replies

You could you delegates and event. This is the simpliest way to do it.
You need any help?

You could you delegates and event. This is the simpliest way to do it.
You need any help?

Yes , please..

(I have 3 more forms those also get updated like the FORM 2 mentioned above)



This is a simple example of how to do this with events/delegates:

In Form1:

//Declare the delegate that will point to the text-setting method
        public delegate void TextChangeHandler(object sender, string s);
        //Declare the event that is to be raised when the text changes
        public event TextChangeHandler TextChange;

        //This button raises the TextChange event
        private void button1_Click(object sender, EventArgs e)
            TextChange(sender, textBox1.Text);
        //This button adds a new Form2 to the project, and registers 
        //its text changing method to be called when the textchange event
        private void button2_Click(object sender, EventArgs e)
            //Create the form, and using a CTOR set the initial text
            Form2 newForm = new Form2(textBox1.Text);
            //Add the textchanged event to the new form
            TextChange += new TextChangeHandler(newForm.TextChangedEvent);

In Form2:

//CTOR - takes a string to initialize the label
        public Form2(string s)
        //This is the event that handles the changed text event from Form1
        public void TextChangedEvent(object sender, string s)
        //This is the actual method that changes the text (in this case, a label) 
        private void SetText(string s)
            label1.Text = s;

This is my understanding of events, anyway (and it works). If I did something wrong, please feel free to correct me.

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