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C# Event name is null

I have a WinForms application wherein I have my main application with a separate class that is part of the solution. In the class which is defining a User control with Dev Express buttons, I have defined my event delegate, event, method and eventargs.
In the main program, i have defined my listener.
I am getting a null value in my event method and cannot see why. I have reviewed this a number of times and as far as I can see, it is completely correct.
I would appreciate any comments/corrections that would be useful here.
This is the code in my class.
public partial class XtraUserControl1 : XtraUserControl, IAnyControlEdit
{
public delegate void ButtonClickedEventHandler(object sender, ClickEventArgs e);
public event ButtonClickedEventHandler ButtonClicked;
public XtraUserControl1()
{
InitializeComponent();
}
public void OnButtonClicked(ClickEventArgs e)
{
if (ButtonClicked != null)
{
ButtonClicked(this, e);
}
}
public class ClickEventArgs : EventArgs
{
public readonly SimpleButton buttonClicked;
public ClickEventArgs(SimpleButton button)
{
this.buttonClicked = button;
}
}
This is the main code where I have defined the listener.
private void frmEHHeaders_Load(object sender, EventArgs e)
{
// Create the button group from the User Control XtraUserControl1 and add it to the grid repository
btnGroup = new User_Controls.XtraUserControl1();
RepositoryItemAnyControl riAny = new RepositoryItemAnyControl();
riAny.Control = btnGroup;
grdEHHeaders.RepositoryItems.Add(riAny);
colButtons.ColumnEdit = riAny;
// Add event handlers
this.grdEHHeaders.Views[0].MouseDown += gridView1_MouseDown;
gridView1.CustomRowCellEdit += GridView1_CustomRowCellEdit;
// Listener for the button class
btnGroup.ButtonClicked += new User_Controls.XtraUserControl1.ButtonClickedEventHandler(btnGroup_ButtonClicked);
GetData();
}
private void btnGroup_ButtonClicked(object sender, User_Controls.XtraUserControl1.ClickEventArgs e )
{
SimpleButton myButton = e.buttonClicked;
MessageBox.Show("You clicked " + myButton.Text);
}

c# execute a method from Form in the MainForm [duplicate]

I am working with windowsFrom in c#. I am trying to call mainfrom method in one of the from in user control.
I have mainfrom like this
namespace Project
{
public partial class MainForm : Form
{
public MainForm()
{
InitializeComponent();
}
public void TempCommand()
{
StartTemp();
}
}
}
I have the button click in the user control. When i click that button then it will open another form. I have the code like this in the user control.
private TempCalib _tempCalib = new TempCalib();
private void calibBtn_Click(object sender, EventArgs e)
{
_tempCalib.Show();
}
it will open another from and i have one button in that from. I need to call mainfrom method when i click "Ok" button in this from.
namespace Project
{
public partial class TempCalib : Form
{
public TempCalib()
{
InitializeComponent();
}
private void OkButton_Click(object sender, EventArgs e)
{
// I need to call the mainfrom "TempCommand" method here.
this.Hide();
}
}
}
Can anyone help me how to do this.
Thanks.

Quick answer
Just add a reference to the primary form in your secondary form:
public partial class TempCalib : Form
{
private MainForm _main
public TempCalib(MainForm main) : this()
{
_main = main;
}
/// Other stuffs
}
Then assign value when you construct your secondary form:
private TempCalib _tempCalib;
private void calibBtn_Click(object sender, EventArgs e)
{
if (_tempCalib == null)
_tempCalib = new TempCalib(this);
_tempCalib.Show();
}
If calibBtn_Click isn't inside MainForm (but it's inside a UserControl on it) then you can replace _tempCalib initialization with:
_tempCalib = new TempCalib((MainWindow)FindForm());
You'll be then able to call the primary form:
private void OkButton_Click(object sender, EventArgs e)
{
_main.TempCommand();
this.Hide();
}
Notes: this is just one option, you may create a property to hold MainForm reference (so secondary form can be reused and it'll be more designer friendly) moreover TempCalib is not an UserControl but a Form (pretty raw but for an UserControl you may just check its parent Form and cast it to proper type).
Improvements
Such kind of references are often an alert. Usually UI components shouldn't not be so coupled and a public Form's method to perform something very often is the signal that you have too much logic in your Form. How to improve this?
1. DECOUPLE CONTROLS. Well a first step may be to decouple them a little bit, just add an event in TempCalib and make MainForm its receiver:
public partial class TempCalib : Form
{
public event EventHandler SomethingMustBeDone;
private void OkButton_Click(object sender, EventArgs e)
{
OnSomethingMustBeDone(EventArgs.Empty); / TO DO
this.Hide();
}
}
Then in MainForm:
private TempCalib _tempCalib;
private void calibBtn_Click(object sender, EventArgs e)
{
if (_tempCalib == null)
{
_tempCalib = new TempCalib();
_tempCalib.SomethingMustBeDone += _tempCalib_SomethingMustBeDone;
// In _tempCalib_SomethingMustBeDone you'll invoke proper member
// and possibly hide _tempCalib (remove it from OkButton_Click)
}
_tempCalib.Show();
}
2. DECOUPLE LOGIC FROM CONTROLS. UI changes pretty often, logic not (and when it changes probably isn't in parallel with UI). This is just the first step (now TempCalib isn't aware of who will use it). Next step (to be performed when too much things happen inside your form) is to remove this kind of logic from the form itself. Little example (very raw), keep TempCalib as before (with the event) and change MainForm to be passive:
public partial class MainForm : Form
{
public event EventHandler Calibrate;
protected virtual void OnCalibrate(EventArgs e)
{
// TODO
}
}
Now let's create a class to control the flow and logic:
public class MyTaskController
{
private MainForm _main;
private TempCalib _tempCalib;
public void Start()
{
_main = new MainForm();
_main.Calibrate += OnCalibrationRequested;
_main.Show(); // Or whatever else
}
private void OnCalibrationRequested(object sender, EventArgs e)
{
if (_tempCalib == null)
{
_tempCalib = new TempCalib();
_tempCalib.SomethingMustBeDone += OnSomethingMustBeDone();
}
_tempCalib.Show();
}
private OnSomethingMustBeDone(object sender, EventArgs e)
{
// Perform the task here then hide calibration window
_tempCalib.Hide();
}
}
Yes, you'll need to write much more code but this will decouple logic (what to do as response to an action, for example) from UI itself. When program grows up this will help you to change UI as needed keeping logic unaware of that (and in one well defined place). I don't even mention that this will allow you to use different resources (people) to write logic and UI (or to reuse logic for different UI, WinForms and WPF, for example). Anyway IMO the most obvious and well repaid benefit is...readability: you'll always know where logic is and where UI management is, no search, no confusion, no mistakes.
3. DECOUPLE LOGIC FROM IMPLEMENTATION. Again you have more steps to perform (when needed). Your controller is still aware of concrete types (MainForm and TempCalib). In case you need to select a different form at run-time (for example to have a complex interface and a simplified one or to use dependency injection) then you have to decouple controller using interfaces. Just an example:
public interface IUiWindow
{
void Show();
void Hide();
}
public interface IMainWindow : IUiWindow
{
event EventHandler Calibrate;
}
public interface ICalibrationWindow : IUiWindow
{
event EventHandler SomethingMustBeDone;
}

You could use a custom event that is declared in your UserControl. Then your form needs to handle this event and call the method you want to call. If you let the UserControl access your form, you are hard-linking both with each other which decreases reusability of your UserControl.
For example, in TempCalib:
public delegate void OkClickedHandler(object sender, EventArgs e);
public event OkClickedHandler OkClicked;
private void OkButton_Click(object sender, EventArgs e)
{
// Make sure someone is listening to event
if (OkClicked == null) return;
OkClicked(sender, e);
this.Hide();
}
in your mainform:
private void Mainform_Load(object sender, EventArgs e)
{
_tempCalib.OkClicked += CalibOkClicked;
}
private void CalibOkClicked(Object sender, EventArgs e)
{
StartTemp();
}

You create an event in your usercontrol and subscribe to this in the mainform.
That is the usual way.

Form1 Code:
UserControl1 myusercontrol = new UserControl1();
public void TabClose(Object sender,EventArgs e)
{
int i = 0;
i = tabControl1.SelectedIndex;
tabControl1.TabPages.RemoveAt(i);
}
private void Form1_Load(object sender, EventArgs e)
{
myusercontrol.Dock = DockStyle.Fill;
TabPage myTabPage = new TabPage();
myTabPage.Text = "Student";
myTabPage.Controls.Add(myusercontrol);
tabControl1.TabPages.Add(myTabPage);
myusercontrol.OkClick += TabClose;
}
UserControl1 Code:
public delegate void OkClickedHandler(Object sender, EventArgs e);
public partial class UserControl1 : UserControl
{
public event OkClickedHandler OkClick;
public UserControl1()
{
InitializeComponent();
}
private void button3_Click(object sender, EventArgs e)
{
if (OkClick == null) return;
OkClick(sender, e);
}
}

Try this:
From user control try this:
MainForm form = this.TopLevelControl as MainForm;
form.TempCommand();

Custom user control doesn't catch any mouse events in c#

I create a custom user control and use that in my form.
but it does not capture any mouse event!
what is the problem?
thanks

Define the event in your custom control
private delegate void MyClickEvent(object sender, EventArgs e);
public event MyClickEvent MyClick;
public void OnMyClickEvent(object sender, EventArgs e)
{
if (MyClick != null)
MyClick(sender, e);//execute event
}
Now in MainForm
public partial class Form1
{
public Form1()
{
myCustomButton.MyClick += FireThisOnClick;
}
private void FireThisOnClick(object sender, EventArgs e)
{
//this will be executed on click
}
}

call event from form2 in form1

hi
call event from form2 in form1?
for example :
The following code into form2 :
private void Form2_Load(object sender, EventArgs e)
{
MessageBox.Show("http://stackoverflow.com");
}
What to write in a form1?

Why are you wanting to call the event? Will you know the sender and the Event Args?
Why don't you just create a public method in Form2 that Form1 is able to see?

how about form2.Form2_Load(this, null)

You can't call private members of a class from outside it.
You can change the accessibility to internal, which will make it visible within the assembly - if your form1 is in the same assembly.
Alternatively you can make it a public method, which would make it globally accessible.
However, you shouldn't call event handlers in such a manner - they are supposed to handle events that the declaring class raises.
For the sample code you gave, a better solution would be to create a public or internal method that can be called from this event handler:
private void Form2_Load(object sender, EventArgs e)
{
MyMethod();
}
public MyMethod()
{
MessageBox.Show("http://stackoverflow.com");
}
In order to call this method from form1, it needs to know about form2:
// in form1
Form frm2 = new Form2();
frm2.MyMethod();

You can't raise an Event from outside a class.
The convention is that you call a OnEventname method in the class. Usually this method is protected (can't only accessed from the class itself or others that inherit from it)
// in form1
private void Method1()
{
using (var form2 = new Form2())
{
form2.Show();
form2.RaiseLoadEvent(EventArgs.Empty);
}
}
// Create this method in form2
public void RaiseLoadEvent(EventArgs e)
{
OnLoad(this, e);
}
// The OnLoad method already exists in form 2
// But it usually looks like this
protected void OnLoad(EventArgs e)
{
var eh = LoadEventHandler;
if (eh != null)
{
eh(this, e);
}
}
But I don't suggest to raise the LoadEvent, because It is raised only once after the creation of the form. More usual is to react to the Load event to modify the form.
privat void Method1()
{
using (var form2 = new Form2())
{
// Add Event Handler
form2.Load += new EventHandler(form2_Load);
form2.ShowDialog();
}
// Allways remove Event Handler to avoid memory leaks
form2.Load -= new EventHandler(form2_Load);
}
private void form2_Load(object sender, EventArgs e)
{
form2.Text = "Hello from form1";
}

Form1 (the event publisher) should expose a separate, public event property for Form2 (the subscriber) to subscribe to.
For example: the form publishing the event will look like this:
public partial class Publisher : Form
{
public event PostUpdateHandler OnPostUpdate;
public Publisher()
{
InitializeComponent();
new Subscriber(this).Show();
}
private void button1_Click(object sender, EventArgs e)
{
if (OnPostUpdate != null)
{
OnPostUpdate(new PostUpdateArgs(textBox1.Text));
}
}
}
public delegate void PostUpdateHandler(PostUpdateArgs args);
public class PostUpdateArgs : EventArgs
{
public string UpdateText;
public PostUpdateArgs(string s)
{
UpdateText = s;
}
}
The subscribing form looks like this:
public partial class Subscriber : Form
{
public Subscriber()
{
InitializeComponent();
}
public Subscriber(Publisher publisher) : this()
{
publisher.OnPostUpdate += new PostUpdateHandler(publisher_OnPostUpdate);
}
private void publisher_OnPostUpdate(PostUpdateArgs args)
{
this.Form2_Load(null, null);
}
private void Subscriber_FormClosed(object sender, FormClosedEventArgs e)
{
this.Dispose();
}
private void Form2_Load(object sender, EventArgs e)
{
MessageBox.Show("http://stackoverflow.com");
}
}
When the user presses button1 on the publishing form, the subscribing form will execute the code associated with the delegate, resulting in a message box popping up with the message http://stackoverflow.com.

Listening to Events in Main Form from Another Form in C#

I have an application that has a main form and uses an event handler to process incoming data and reflect the changes in various controls on the main form. This works fine.
I also have another form in the application. There can be multiple instances of this second form running at any given time.
What I'd like to do is have each instance of this second form listen to the event handler in the main form and update controls on its instance of the second form.
How would I do this?
Here's some sample code. I want to information from the_timer_Tick event handler to update each instance of SecondaryForm.
public partial class Form1 : Form
{
Timer the_timer = new Timer();
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
the_timer.Tick += new EventHandler(the_timer_Tick);
the_timer.Interval = 2000;
the_timer.Enabled = true;
}
void the_timer_Tick(object sender, EventArgs e)
{
// I would like code in here to update all instances of SecondaryForm
// that happen to be open now.
MessageBox.Show("Timer ticked");
}
private void stop_timer_button_Click(object sender, EventArgs e)
{
the_timer.Enabled = false;
}
private void start_form_button_Click(object sender, EventArgs e)
{
SecondaryForm new_form = new SecondaryForm();
new_form.Show();
}
}

class SecondForm
{
private FirstForm firstForm;
public SecondForm()
{
InitializeComponent();
// this means unregistering on form closing, uncomment if is necessary (anonymous delegate)
//this.Form_Closing += delegate { firstForm.SomeEvent -= SecondForm_SomeMethod; };
}
public SecondaryForm(FirstForm form) : this()
{
this.firstForm = form;
firstForm.Timer.Tick += new EventHandler(Timer_Tick);
}
// make it public in case of external event handlers registration
private void Timer_Tick(object sender, EventArgs e)
{
// now you can access firstForm or it's timer here
}
}
class FirstForm
{
public Timer Timer
{
get
{
return this.the_timerl
}
}
public FirstForm()
{
InitializeComponent();
}
private void Button_Click(object sender, EventArgs e)
{
new SecondForm(this).ShowDialog(); // in case of internal event handlers registration (in constructor)
// or
SecondForm secondForm = new SecondForm(this);
the_timer.Tick += new EventHandler(secondForm.Timer_tick); // that method must be public
}

Consider using loosely coupled events. This will allow you to couple the classes in such a way that they never have to be directly aware of each other. The Unity application block comes with an extension called EventBroker that makes this very simple.
Here's a little lick of the sugar:
public static class EVENTS
{
public const string UPDATE_TICKED = "event://Form1/Ticked";
}
public partial class Form1 : Form
{
[Publishes(EVENTS.UPDATE_TICKED)]
public event EventHandler Ticked;
void the_timer_Tick(object sender, EventArgs e)
{
// I would like code in here to update all instances of SecondaryForm
// that happen to be open now.
MessageBox.Show("Timer ticked");
OnTicked();
}
protected virtual void OnTicked()
{
if (Ticked == null) return;
Ticked(this, e);
}
}
public partial class SecondaryForm : Form
{
[SubscribesTo(EVENTS.UPDATE_TICKED)]
private void Form1_Ticked(object sender, EventHandler e)
{
// code to handle tick in SecondaryForm
}
}
Now if you construct both of these classes using Unity, they will automatically be wired together.
Update
Newer solutions use message bus to handle loosely coupled events. See http://masstransit-project.com/ or http://nimbusapi.github.io/ as examples.

I guess you can make SecondaryForm take in the parent form in the constructor, and the add an event handler in the constructor.
private void start_form_button_Click(object sender, EventArgs e)
{
SecondaryForm new_form = new SecondaryForm(this);
new_form.Show();
}
In SecondaryForm.cs:
public SecondaryForm(ISomeView parentView)
{
parentView.SomeEvent += .....
}