Develop Reference

C# Event driving between user controls on win forms

I have a main form (form1) which has a panel (panel1) -- see pic.
Form1 pic
Panel1 loads one of two different user controls based on which button is pressed (to simulate screen changes). I have a button on user control 1 which needs to act (change text) on user control 2.
The issue I have is the user controls are dynamically created with a button press on form 1 (see code below) which is causing me issues trying to link events-
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
panel1.Controls.Add(new Screens.UC1());
}
private void button1_Click(object sender, EventArgs e)
{
foreach (Control ctrl in panel1.Controls)
{
ctrl.Dispose();
}
panel1.Controls.Add(new Screens.UC1());
}
private void button2_Click(object sender, EventArgs e)
{
foreach (Control ctrl in panel1.Controls)
{
ctrl.Dispose();
}
panel1.Controls.Add(new Screens.UC2());
}
}
What is the best way to deal with linking these kinds of items with events when the instance of the objects are dynamically created. I also tried making instances of the screen and then referencing to those, but that ran into scope issues.
Code for UC1 (user control 1)
public partial class UC1 : UserControl
{
public UC1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
//Event to change text on UC2
}
}
Code for UC2 (user control 2)
public partial class UC2 : UserControl
{
public UC2()
{
InitializeComponent();
}
public void WriteText(object sender, EventArgs e)
{
label2.Text = "Text Changed...";
}
}
Any help greatly appreciated.

Why dispose and create all those controls when the operator presses a button?
Better is to create two UserControls. One with all the Controls you want to show when operator presses button 1 and one with all the Controls you want to show when operator presses button 2.
To create a user control use menu Project - Add User Control, or right click in solution explorer on your project and select add new item.
Layout your user controls with all the controls your want to show. Add event handlers etc.
Then in your form:
private readonly UserControl userControl!;
private readonly UserControl userControl2;
public MyForm()
{
InitializeComponent()
this.userControl1 = new UserControlA(...);
this.userControl2 = new UserControlB(...);
// make sure that the user controls are Disposed when this form is Disposed:
this.Components.Add(this.userControl1);
this.Components.Add(this.userControl2);
}
void OnButton1Clicked(object sender, ...)
{
// remove userControl2 from the panel
this.Panel1.Controls.Remove(this.userControl2);
// add userControl1 to the panel
this.Panel1.Controls.Add(this.userControl1);
}
This way all the overhead of creating / adding / positioning / add event handlers and all cleanup is only done once: during construction of your form. Switching the user controls will be done in a flash

I am not sure what you are trying to accomplish, but it looks like you are trying to change the state of objects from other objects that cannot have references to the objects they are trying to change.
In this case, I would create a type that functions as some kind of manager that subscribes to events of all of these controls. You can create your own events within a UC class, or just use the Windows Forms click event like you are already doing.
Since the handler of the events are defined in the manager, you can easily write logic that will work on the other user controls, as long as the manager has references to them.
Like this:
public class ClickTrafficer {
private UC target;
public void HandleClick(object sender, UCClickHandlerEventArgs ea) {
target.WriteText(ea.TextToWrite);
}
}
public Form1()
{
InitializeComponent();
var trafficer = new ClickTrafficer();
var screen1 = new Screens.UC1();
screen1.Click += trafficer.HandleClick;
panel1.Controls.Add(screen1);
}
This is a crude idea of what you could do. Missing here are the logic to set whatever the target field must be set to. You need to create logic that tells the trafficer which control sets which control's text.
Also, the ClickTrafficer I created uses a custom event with custom eventargs, you need to define those or find a way to pass the necessary information through the built in events. Creating events is really easy though so you can look that up online.

Passing data from a UserControl to another

I have a form and two custom UserControl that I made myself. one control has some buttons that each of these button have theire Tag property set to an array of PointF. I have another UserControl that has a ObservableCollection<PointF[]> that I set its event handler to draw the lines if data is being added to it. This works fine If I put the data points on its own class...just make to sure it works.
No my problem is, having this two control in one form, how can I set the click event of buttons in the first control, to add data points to the second control?
This two controls are both in two different projects in my soloution. and the form that these to controls are being showed in, is also in a different project (it is the launching project of soloution)

Add an event to the first control.
public event EventHandler<EventArgs> Control1ButtonClicked;
private void OnClicked()
{
var handler = Control1ButtonClicked;
if (handler != null)
{
handler(this, new EventArgs());
}
}
private void Button1_Click(object sender, EventArgs e)
{
OnClicked();
}
Add a property to the second control
public ObservableCollection<PointF[]> MyPoints{ get; set;};
Then in your main application add a listener
userControl1.Control1ButtonClicked += new EventHandler<EventArgs>(userControl1_Control1ButtonClicked);
void userControl1_Control1ButtonClicked()
{
//Do Something to control 2
userControl2.MyPoints.Add() = //Whatever
}

You could add a public method on the second usercontrol that receive an array of PointF, then inside this method you could add the PointF to your collection.
EDIT: To handle the click event inside the first user control
inside the first usercontrol add the event and the delegate required
public delegate void OnClickPointDataEvent(object sender, PointF[] data);
public event OnClickPointDataEvent ClickPointData;
then form_load event subscribe to the usercontrol1 event
uc1.ClickPointData += new UserControl1.OnClickPointDataEvent(form_subscribe_event);
private void form_subscribe_event(object sender, PointF[] data)
{
uc2.SomePublicMethod(data);
}
and finally, inside the first usercontrol button click call the code that handle the event inside the form
....
if(ClickPointData != null)
ClickPointData(pointf_array);
...

C# delegate to notify changes

How can I notify an outside "source" of the changes I make using a delegate.
Basically I have a form, I fill in that form and click a button that saves
my filled in data into a DB table as an XML. I want to be able to notify that the changes to the form have been made using a delegate that another "entity" can invoke.
public void Changes_Made()
{
//yay. Changes made.
}
protected void okButton_Click(object sender, EventArgs e)
{
//...
//save data
//...
Changes_Made();
}
Practical scenario is: as i save my preferences, the grid that shows my data will refresh and use the preferences set when i click the ok_button. Does this make any sense?

You can raise a event for notifying the changes.
public ctor() // Method where you want to hook the event, can be constructor or any thing else
{
//Hook to event
obj.ChangesMade += Changes_Made;
// Here obj is the object of type in which you have okButton_Click
// and ChangesMade event declaration
}
public void Changes_Made()
{
//yay. Changes made. update grid
}
//declare event
public event EventHandler ChangesMade();
protected void okButton_Click(object sender, EventArgs e)
{
//...
//save data
//...
//raise event
if(ChangesMade != null)
ChangesMade(this, new EventArgs());
}

that's what C# events are for.

If I understand you correctly, the grid, and the save button are on the same page. If that's the case, simply call PopulateGridData();, or something like that directly after you saved the changes.

Accessing Form's Control from Custom Control

I want to access the list box and add the item into it for my Custom control which is dynamically created on run time. I want to add the Item when I press the button place in the custom control, but it does not work. I have use the following code to work:
private void button1_Click(object sender, EventArgs e)
{
Form1 frm = new Form1();
frm.ABC = "HI";
}
the 'ABC' is the Public string on the form ie:
public string ABC
{
set { listBox1.Items.Add (value); }
}
the above string works fine when I use it form the Button on the form and it adds the value in the lsitbox but whent I use it form the custom control's button the text of the 'value' changes but it does not add the item in list box.I have also try it on tabel but does not help. I change the Modifires of the ListBox1 from Private to Public but it does not works. The above function works well in the form but cannot work from the custom control.
Thanks.

Expose an event ("ItemAdded" or whatever) in the child form that your main form can handle. Pass the data to any event subscribers through an EventArgs derived object. Now your mainform can update the UI as it please with no tight coupling between the two classes. One class should not know about the UI layout of another, it's a bad habit to get into (one that everyone seems to suggest when this question crops up).

What I think you should use is
this.ParentForm
So in your case it should be:
public string ABC
{
set { this.ParentForm.listBox1.Items.Add (value); }
}

The easiest way would be to pass the form down into your custom control as a parameter in the constructor that way you could access it from the custom control.
EX:
public class CustomControl
{
private Form1 _form;
public CustomControl(Form1 form)
{
_form = form;
}
private void button1_Click(object sender, EventArgs e)
{
_form.ABC = "HI";
}
}

How to change text in a textbox on another form in Visual C#?

In Visual C# when I click a button, I want to load another form. But before that form loads, I want to fill the textboxes with some text. I tried to put some commands to do this before showing the form, but I get an error saying the textbox is inaccessible due to its protection level.
How can I set the textbox in a form before I show it?
private void button2_Click(object sender, EventArgs e)
{
fixgame changeCards = new fixgame();
changeCards.p1c1val.text = "3";
changeCards.Show();
}

When you create the new form in the button click event handler, you instantiate a new form object and then call its show method.
Once you have the form object you can also call any other methods or properties that are present on that class, including a property that sets the value of the textbox.
So, the code below adds a property to the Form2 class that sets your textbox (where textbox1 is the name of your textbox). I prefer this method method over making the TextBox itself visible by modifying its access modifier because it gives you better encapsulation, ensuring you have control over how the textbox is used.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string TextBoxValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
And in the button click event of the first form you can just have code like:
private void button1_Click(object sender, EventArgs e)
{
Form2 form2 = new Form2();
form2.TextBoxValue = "SomeValue";
form2.Show();
}

You can set "Modifiers" property of TextBox control to "Public"

Try this.. :)
Form1 f1 = (Form1)Application.OpenForms["Form1"];
TextBox tb = (TextBox)f1.Controls["TextBox1"];
tb.Text = "Value";

I know this was long time ago, but seems to be a pretty popular subject with many duplicate questions. Now I had a similar situation where I had a class that was called from other classes with many separate threads and I had to update one specific form from all these other threads. So creating a delegate event handler was the answer.
The solution that worked for me:
I created an event in the class I wanted to do the update on another form. (First of course I instantiated the form (called SubAsstToolTipWindow) in the class.)
Then I used this event (ToolTipShow) to create an event handler on the form I wanted to update the label on. Worked like a charm.
I used this description to devise my own code below in the class that does the update:
public static class SubAsstToolTip
{
private static SubAsstToolTipWindow ttip = new SubAsstToolTipWindow();
public delegate void ToolTipShowEventHandler();
public static event ToolTipShowEventHandler ToolTipShow;
public static void Show()
{
// This is a static boolean that I set here but is accessible from the form.
Vars.MyToolTipIsOn = true;
if (ToolTipShow != null)
{
ToolTipShow();
}
}
public static void Hide()
{
// This is a static boolean that I set here but is accessible from the form.
Vars.MyToolTipIsOn = false;
if (ToolTipShow != null)
{
ToolTipShow();
}
}
}
Then the code in my form that was updated:
public partial class SubAsstToolTipWindow : Form
{
public SubAsstToolTipWindow()
{
InitializeComponent();
// Right after initializing create the event handler that
// traps the event in the class
SubAsstToolTip.ToolTipShow += SubAsstToolTip_ToolTipShow;
}
private void SubAsstToolTip_ToolTipShow()
{
if (Vars.MyToolTipIsOn) // This boolean is a static one that I set in the other class.
{
// Call other private method on the form or do whatever
ShowToolTip(Vars.MyToolTipText, Vars.MyToolTipX, Vars.MyToolTipY);
}
else
{
HideToolTip();
}
}
I hope this helps many of you still running into the same situation.

In the designer code-behind file simply change the declaration of the text box from the default:
private System.Windows.Forms.TextBox textBox1;
to:
protected System.Windows.Forms.TextBox textBox1;
The protected keyword is a member access modifier. A protected member is accessible from within the class in which it is declared, and from within any class derived from the class that declared this member (for more info, see this link).

I also had the same doubt, So I searched on internet and found a good way to pass variable values in between forms in C#, It is simple that I expected. It is nothing, but to assign a variable in the first Form and you can access that variable from any form. I have created a video tutorial on 'How to pass values to a form'
Go to the below link to see the Video Tutorial.
Passing Textbox Text to another form in Visual C#

private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2();
TextBox txt = (TextBox)frm.Controls.Find("p1c1val", true)[0];
txt.Text = "foo";
}