In C# I have two forms "Form1" and "Form2". Form1 creates images that are stored in a folder. Form2 displays the number of images in that folder.
Say I have made 2 images with Form1 and then I open Form2. Form2 now says there are 2 images. Now while keeping both forms open I want to be able to add a new image and Form2 updates. At the moment if I use Form1 to add more images while Form2 is open Form2 continues to display the number of images that were in the folder when Form2 opened.
I have found solutions that involve Form2 closing and reopening but I don't want this. It's jarring for the user having windows opening and closing every time they press a button. I just want Form2 to update live as I make changes with Form1.
Any help would be greatly appreciated!! Thanks!
You can do this with public method in Form2
In Form1 you need to save Form2 object in property
FORM 1
public partial class Form1 : Form
{
public Form2 MyProperty { get; set; }
public Form1()
{
InitializeComponent();
}
// for opening form 2
private void button1_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2();
f2.Show();
MyProperty = f2;
}
// adding new image
private void button_ADD_Click(object sender, EventArgs e)
{
MyProperty.updateCounter();
}
}
When you add new image, then you can call the metoh from Form2 to update counter.
In FORM 2 you need crate PUBLIC method to update counter
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
// default value
label1.Text = "0";
}
// update counter
public void updateCounter()
{
label1.Text = (int.Parse(label1.Text) + 1).ToString();
}
}
You may want to take a look at events and delegates. Basically, whenever you do something to Form1 that can affect other forms, you want to trigger an event. In Form2, you have a method which you call whenever that event triggers. This way you can have multiple forms open, and as long as you set them to "listen" to a given event, they can all react.
You can read more about them here, in the Microsoft Documentation.
Related
I am trying to have a button in Form3 change a label's text in Form1 and Form2.
I have gotten it to work somewhat but in order to have the label change I have to have the mouse click on it. This is my current code in form 1 and 2:
label1.Text = Form3.myNameClass.myName;
and this is code in form 3
public class tournamentNameClass
{
public static string tournamentName;
}
public void button1_Click(object sender, EventArgs e)
{
myNameClass.myName = textBox3.Text;
}
How can I make it so that I dont need to press the label to get it to change?
Since you are at the start of learning, I'm not going to go in events and delegates.
My example demonstrates how you manipulate a control on Form1 from Form2 directly. You should be able to figure this out for Form3 easily by yourself, and is together a good practice of understanding.
(I want to state that there are many different methods/techniques for passing data or manipulate controls between forms, I guess this is the easiest one for you to understand as a beginner, as this is the most simplistic approach of all)
Form1 Designer
First we make label1 its modifier to Public (so we can reach it in another class) in the designer like so:
Form1 code behind
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
// With the keyword "this" we pass in Form1, the current instance we are in
Form2 form2 = new Form2(this);
form2.Show();
}
}
Form2 code behind
public partial class Form2 : Form
{
private Form1 _form1;
public Form2(Form1 form1)
{
_form1 = form1;
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
_form1.label1.Text = "lets change the text";
}
}
We are passing Form1 completely in the constructor, this could easily be the label1 control alone.
Result
I think you only need to trigger a redraw on forms 1 and 2.
after you set the text of the label, try calling labelControl.Refresh()
Or you could call refresh on form1 and form2 if that's any easier (that is a bit heavy handed though)
This will instruct the forms to redraw their visual representation based on how the data is set in the form currently.
Update:
You will need to invert your logic somewhat..
Rather than having a reverence to form 3 from form 1 and form 2, you will need to have a reference to form 1 and 2 from form3.. (woah so many form)
So then your button click method would look like this
public void button1_Click(object sender, EventArgs e)
{
form1.label1.Text = textBox3.Text;
form2.label1.Text = textBox3.Text;
form1.label1.Refresh();
form2.label1.Refresh();
}
So, I have a Form2 with the method public void LoadTree() (which loads data from a database onto a TreeView in Form2), I also have a Form3 that starts on a button click from Form2. In Form3 on a button click (after some code executes) I want to use the LoadTree() method from Form2.
I have the following code in Form3 to do this:
private void button1_Click(object sender, EventArgs e)
{
var loading = new Form2();
loading.LoadTree();
loading.Show();
}
All works and executes well,no errors, but at the end of this I have a Form2, a Form3, and another Form2, If i try to put a code to close the first Form2, the entire program shuts down, what could I do about it?, I just want that after I click the button on Form3, Form2 to show as updated.
I have a Form2 with the method public void LoadTree() (which loads
data from a database onto a TreeView in Form2
Do not make database calls directly in a form. Put this code in another class, better yet use n-tier.
In Form3 on a button click (after some code executes) I want to use
the LoadTree() method from Form2.
And
I just want that after I click the button on Form3, Form2 to show as
updated.
Form3 raises the event which is to be handled by Form2. Best practice is to use events for communicating messages across forms. You could use a property here, but this would be a side effect of a property and thus not a good way to accomplish the goal.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void LoadTree(Object o, EventArgs e)
{
//do work
MessageBox.Show("Loading tree...");
}
private void button1_Click(object sender, EventArgs e)
{
var form = new Form3();
form.LoadTreeEvent += form_LoadTreeEvent;//Hook into the Form3 event
form.Show();
}
void form_LoadTreeEvent(object o, EventArgs e)
{
LoadTree(o, e);//Handle Form3 Event
}
}
public partial class Form3 : Form
{
//The event is raised by Form3, however it's handled by Form2.
public event LoadTreeHandler LoadTreeEvent;
public delegate void LoadTreeHandler(Object o, EventArgs e);
public Form3()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
LoadTreeEvent(null, null);//Raise the event in Form3 and pass whatever
//do work...maybe close this form??
}
}
Problem : You are creating the newinstance of Form2 (or whichever Form you want to show) everytime, so that it creates a new instance everytime and all your old changes will notbe available.
Solution : Don't create a new instance of Forms which are hidden while switching between the different Forms,rather open the already existing Form2 from Memory using the Application.OpenForms[]
Try This:
Form2 form2 = (Form2) Application.OpenForms["Form2"];
//now use form2 variable
form2.LoadTree();
form2.Show();
In my main form (form1) I have checkboxes that when checked should also check the corresponding box in form2. I also want if checkboxes in form2 are checked they check the corresponding boxes on form1. The problem that I believe I am encountering is that form1 can make an object of form2 to reference, however if I instantiate an object of form1 within form2 I believe it creates an infinite loop? Any help figuring this out is appreciated.
Form1 creates an object of form2:
Form2 formSettings = new Form2();
Now when I have an event I can update form2:
public void logScanResultsToolStripMenuItem_Click(object sender, EventArgs e)
{
if (logScanResultsToolStripMenuItem.Checked)
{
formSettings.chbxLogScanResults.Checked = true;
}
else
{
formSettings.chbxLogScanResults.Checked = false;
}
}
But if I try to do something similar in Form2:
Form1 form1 = new Form1();
So that I can reference form1's menu item from within form2(formSettings) I end up creating an object (form1) that calls to make an object of Form1, which within Form1 includes a call to create an object of Form2 and thus an endless loop.
You shouldn't create an instance every time a checkbox is checked off. You need to maintain the instances alive and hide/show them as needed. Also, the constructor of one of the forms should receive the other one as parameter in its constructor so they can reference each other.
Hopefully this is clear enough. It isn't a straight out answer as you really dont have much detail in your question.
Basically you have two forms, Form1 and Form2, which will be throwing events (OnChangeEvent?) on the change of some checkboxes.
Form1 listens for events from Form2 and Form2 does the same from Form1.
If Form1's event listen receives a OnChangeEvent and changes its checkbox then it should raise an OnChangeEvent. If on the other hand it doesn't change its checkbox (as it already has the correct value) then it should not raise an OnChangeEvent.
In the body of Form1 you need to declare Form2 to hold an instance of it for referencing and to open it. When you call the Form2.Show method from Form1, you will pass a reference of itself to Form2 which you then can use to gain access back to Form1.
public partial class Form1 : Form
{
Form2 form2 = new Form2();
public Form1()
{
InitializeComponent();
}
private void form1Button_Click(object sender, EventArgs e)
{
form2.Show(this);
}
private void form1CheckBox_CheckedChanged(object sender, EventArgs e)
{
form2.ChangeCheck(form1CheckBox.Checked);
}
public void ChangeCheck(bool isItChecked)
{
form1CheckBox.Checked = isItChecked;
}
}
In Form2 you can now reference Form1 as the owner.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void form2CheckBox_CheckedChanged(object sender, EventArgs e)
{
((Form1)this.Owner).ChangeCheck(form2CheckBox.Checked);
}
public void ChangeCheck(bool isItChecked)
{
form2CheckBox.Checked = isItChecked;
}
}
Lets say I have two forms ( Form1 And Form2 ).
Form1 has a PictureBox
Form2 I has an OpenFileDialog
Form1 is the main form, so when I run the project I see Form1.
How can I change the Image in the PictureBox in Form1 from Form2?
How do I pass a value from a child back to the parent form?
Basically, expose the value that gets returned in the open file dialog with some property and let the parent form grab it.
In the Program.cs file you can set any value, either FormOptions to the form's instance .
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
var frm = new Form1();
// Add the code to set the picturebox image url
Application.Run(frm);
}
In addition you can add the Constructor to Form1 and pass the parameter via constructor.
Pass one form as a parameter to a constructor of the second form or add a method that passed the reference. After you have the reference to your form you can do whatever you want with the from.
Whether to share picture box as a public member is up to you. However, I would suggest making a public method SetImage() in the first form. Second form would call form1.SetImage().
[Update]
Wait, why do you need to set image from OpenFileDialog, you just need receive fileName from the dialog, and then open the file and load into the form.
Like this:
private void button1_Click(object sender, EventArgs e)
{
using (var dialog = new OpenFileDialog())
{
var result = dialog.ShowDialog();
if (result != DialogResult.OK)
return;
pictureBox1.Image = Image.FromFile(dialog.FileName);
}
}
This is code inside of Form1.
[Update]
Here is the basic idea how to access one form from another.
public class MyForm1 : Form
{
public MyForm1()
{
InitializeComponent();
}
public void SetImage(Image image)
{
pictureBox1.Image = image;
}
private void button1_Click(object sender, EventArgs e)
{
var form2 = new Form2(this);
form2.Show();
}
}
public class MyForm2 : Form
{
private MyForm1 form1;
public MyForm2()
{
InitializeComponent();
}
public MyForm2(MyForm1 form1)
{
this.form1 = form1;
}
private void button1_Click(object sender, EventArgs e)
{
form1.SetImage(yourImage);
}
}
You can very simply do this.
At first change your code(in Form1) that show Form2 to looks like this:
<variable-of-type-Form2>.ShowDialog(this);
or if you dont want form2 to be modal
<variable-of-type-Form2>.Show(this);
Next when you got path to image, you can access pictureBox like this
((PictureBox)this.Owner.Controls["pictureBox1"]).Image=Image.FromFile(<filename>);
Assume that you have PictureBox on Form1 with name "pictureBox1"
Ideally, you want to structure your code in a ModelViewController pattern. Then, you simply have a reference in your model to the image in the picture box. When interacting with the OpenFileDialog in Form2, you would call your model adapter interfaces hooked into the views (Form1 and Form2) to change the image being held in the model. In short, you need a callback from the view to the model. If you don't want to redesign your code to be MVC, simply have a shared object holding the image reference that both Form1 and Form2 receive in their constructors, so they can both modify it.
This might be a novice question. :). Consider the following scenario.
Suppose we have two windows forms that are already "loaded" (i.e You
can see both the forms)
Form 1 contains a textbox and a "submit" button while the form 2
contains a text lable.
The user can enter a string in the textbox and press submit on
form 1 The lable on form 2 should
be updated with the new text.
What is the best way to achive this? Any formal way to do this? I don't want to increase the variable scopes unnecessarily.
Edit : Both the forms belong to same application
Assuming these forms are part of the same application, you need to have a common data model where you keep your data and then your forms "bind" to this data model. Check out M-V-C or M-V-VM patterns. This would also nicely separate your UI from your data.
Do some research on model view controller pattern and databinding in winforms.
Create a seperate controller class and reference this in the two forms, which implements INotifyPropertyChanged. On the controller, have a property which propagates the changed events from and to the forms.
Form1 triggers Form2 to open. Form2 has overloaded constructor which takes calling form as argument and provides its reference to Form2 members. This solves the communication problem. For example I've exposed Label Property as public in Form1 which is modified in Form2.
With this approach you can do communication in different ways.
Download Link for Sample Project
//Your Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2(this);
frm.Show();
}
public string LabelText
{
get { return Lbl.Text; }
set { Lbl.Text = value; }
}
}
//Your Form2
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private Form1 mainForm = null;
public Form2(Form callingForm)
{
mainForm = callingForm as Form1;
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
this.mainForm.LabelText = txtMessage.Text;
}
}
alt text http://ruchitsurati.net/files/frm1.png
alt text http://ruchitsurati.net/files/frm2.png