Sharing Data between two forms

Question

Hi I am new to 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 (text boxes radio buttons check boxes numeric up-down controls etc) . FORM 1 does some calculations on this data and prepares a text message. I have a class created to do this job and updated Message is with the Class. FORM2 should take this Data 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 a button on FORM 1 to show FORM 2. FORM 1 must update Data on the FORM 2 whenever a new Message is generated provided FORM 2 is either showing or in minimized state. FORM 2 also needs a method to get the message from Form 1 when Form 2 is instanced. Now I have two FORMs ready but question is: 1> How to transfer the message from FORM 1 to FORM 2. Can I access object that holds the Message text from FROM 2? 2> FORM 2 can be opened / minimized / killed. I want FORM 1 to refresh the Rich Text box even if the FORM 2 is in minimized condition. Any help? (Sorry for my bad English it is my Second language) Regards Babali

Narayan · Answer

Hello Friend That is just a sample to show how to use delegate in your scenario  it can be handled . Thanks Narayan

Babali PK · Answer

Hi Naraya I tried your example program it works but only problem I noticed is that  Open Form 2 button when clicked creates a new instance of Form 2 regardless whether Form 2 is already created or not. This mean if one clicks that button repeatedly soon there will be dozens of Form 2. Anyway will check the delegate concept more in deep sounds to be more cleaner method . Thanks once again. Regards

Babali PK · Answer

Thanks Narayan Sounds interesting will check this and share my finding with you. Regards Babali

Babali PK · Answer

Thanks Sam for the inputs. I have a small doubt here  when I create a FORM 2 but keep it hidden means we are consuming System Resources when it is not needed  is it correct? While on the same topic earlier I attempted making FORM 1 as parent and FORM 2 as a child that worked but only problem was FORM 2 always showed behind some controls on FORM 1  a picture box FORM 2 always used to get behind that picture box.I could never get FORM 2 at front so decided to drop MDI scheme. Do you have any suggestion on this? Regards Babali

Narayan · Answer

Hi You can use delegate to hold a reference to that method used for updating data. Its more cleaner way of doing these kind of things. Please take a look at the attached sample. I have two forms form1 and form2 form1 has a combobox and button click the button 2 to open form2. When you change combobox item those text will be changed in form2. Thanks Narayan

Sam Hobbs · Answer

I am not sure what you are doing so I am not sure if my suggestion will work for you but what I would do is in form 1 create an instance of form 2 except the default for form 2 would be that it is hidden (not visible) initially. Then when form 2 is to be shown I would make it visible and then when it is closed I would actually just make it hidden again but not closed. That way there will always be an instance of form 2. If you want to do it the way you are doing it (using Application.OpenForm s) then you can execute Application.OpenForm s without casting to FORM2. Then check the return value of Application.OpenForm s and if it is null then you know not to use that value. If it is not null then it is safe to assume there is not a problem so you can next cast the return value (from Application.OpenForm s) to FORM2.

Babali PK · Answer

Thanks for the suggestion. In the mean time I tried 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) { ShowMessage(messageIn); } 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 If it is not instanced  I don't bother. 2> FORM 2 is already instanced then I must update it. So check that part first as: In FORM1: bool IsOpen = false; foreach (Form f in Application.OpenForms) { if (f.Text == FORM2) { IsOpen = true; // FORM found break; } } // Loop to check next FORM // If FORM2 is already instance 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]; f1.ShowMessage(message); } When user Clicks on the button on FORM1 to view message I first check first the whether the form is already instance or not. If it is there already I call the the method in FORM2 else I instance the FORM2 as: FORM2 frm2 = new FORM2(message);// message goes as FORM2 constructor input argument frm2.Show(); I am a bot worried the use of: FORM2 f1 = (FORM2)Application.OpenForms[FORM2]; Is it safe (legitimate) or it might pose some potentail problem later? Regards Babali

Sam Hobbs · Answer

Create a public method or property in Form 2 that updates its control and then call that from Form 1.