Maybe I'm just an idiot, but I can't seem to find an event that will fire for a textbox at the same time as the leave, but only when the contents of the textbox has changed. Kinda like a combination of textchanged and leave. I can't use textchanged cause it fires on each keystroke. Right now I'm storing the current value of the textbox in a variable and comparing it on the leave event, but it seems really hackish.
Thanks
You can create your own (derived) class which overrides OnEnter, OnLeave and OnTextChanged to set flags and trigger "your" event.
Something like this:
public class TextBox: System.Windows.Forms.TextBox {
public event EventHandler LeaveWithChangedText;
private bool textChanged;
protected override void OnEnter(EventArgs e) {
textChanged = false;
base.OnEnter(e);
}
protected override void OnLeave(EventArgs e) {
base.OnLeave(e);
if (textChanged) {
OnLeaveWithChangedText(e);
}
}
protected virtual void OnLeaveWithChangedText(EventArgs e) {
if (LeaveWithChangedText != null) {
LeaveWithChangedText(this, e);
}
}
protected override void OnTextChanged(EventArgs e) {
textChanged = true;
base.OnTextChanged(e);
}
}
The answer of #Lucero does it's job almost perfectly.
However, it does not handle the case when a user edits the text and finally enters the same value as before. Therefore I created a similar solution for my own (in C++/CLI, but you can easily adapt it to C#):
public ref class EventArgsCTextBox1 : EventArgs
{
public:
String^ PreviousText;
};
public ref class CTextBox1 : Windows::Forms::TextBox
{
public:
virtual void OnEnter (EventArgs^ i_oEventArgs) override;
virtual void OnLeave (EventArgs^ i_oEventArgs) override;
delegate void EventHandlerCTextBox1 (Object^ i_oSender, EventArgsCTextBox1^ i_oEventArgs);
event EventHandlerCTextBox1^ LeaveChanged;
private:
String^ m_sValue;
};
void CTextBox1::OnEnter (System::EventArgs^ i_oEventArgs)
{
TextBox::OnEnter (i_oEventArgs);
m_sValue = this->Text;
}
void CTextBox1::OnLeave (System::EventArgs^ i_oEventArgs)
{
TextBox::OnLeave (i_oEventArgs);
if (m_sValue != this->Text)
{
EventArgsCTextBox1^ oEventArgs = gcnew EventArgsCTextBox1;
oEventArgs->PreviousText = m_sValue;
LeaveChanged (this, oEventArgs);
}
}
Related
I'm fairly new to C# and I'm trying to create a Hangman game in WinForms, I've got the game functionality working, but I'm trying to create a form where the user selects a category and then the word to guess is from the category selected.
I've got a HangEventArgs like below:
public class HangEventArgs : EventArgs
{
public Category WordCategory { get; set; }
}
and a class for the data (I'm hoping to expand it to add more features in the future).
public enum Category
{
// Categories are stores here
}
public class HangData
{
public Category WordCategory { get; protected set; }
public HangData(Category askWhat)
{
WordCategory = askWhat;
}
}
And a class where the words are stored
public static class WordsToGuess
{
public static string[] Capitals =
{
"London",
"Paris" // more words here
}; // more categories here
Finally I have my button click event for all the categories, I've created my own Button as to not use the default EventArgs.
private void bCategory_Click(object sender, HangEventArgs e)
{
MainGame mg = new MainGame(new HangData(e.WordCategory));
mg.ShowDialog();
}
I've been trying to use event handlers like so
public event EventHandler<HangEventArgs>(object sender, HangEventArgs e);
But I'm not sure the proper way to implement this into my code.
If I use
bCapitals.Click += new EventHandler(bCategory_Click);
I get a no overload matches delegate error and I'm stuck on how to fix it. Thanks for the help in advance.
Create your category button like this:
public class CategoryButton : Button
{
protected override void OnClick(EventArgs e)
{
// Just discard the `e` argument and pass your own argument.
base.OnClick(new HangEventArgs { WordCategory = Category.Cities });
}
}
Subscribe the event with:
categoryButton1.Click += CategoryButton1_Click;
Use like this
private void CategoryButton1_Click(object sender, EventArgs e)
{
if (e is HangEventArgs hangEventArgs) {
MessageBox.Show(hangEventArgs.WordCategory.ToString());
}
}
Note that the click mechanism still works as expected. You don't need to fire the event yourself.
Of course you could create your own event; however, then, it must have a different name like HangClick and you must fire it yourself.
public class CategoryButton : Button
{
public event EventHandler<HangEventArgs> HangClick;
protected virtual void OnHangClick(HangEventArgs e)
{
HangClick?.Invoke(this, e);
}
protected override void OnClick(EventArgs e)
{
OnHangClick(new HangEventArgs { WordCategory = Category.Cities });
// Optionally, if you want to preserve the standard click event behaviour:
base.OnClick(e);
}
}
Subscribe with:
categoryButton1.HangClick += CategoryButton1_HangClick;
Use like this:
private void CategoryButton1_HangClick(object sender, HangEventArgs e)
{
MessageBox.Show(e.WordCategory.ToString());
}
I need to Raise an Event from another Class - i know that this is not possible - but I need a workaround for this.
For now Im doing the following
This is the class, which have to raise the event
internal class DataTransfer
{
public delegate void EventHandler(object sender, OnReaderCommonEventArgs e);
public event EventHandler _OnSerialNumber;
public event EventHandler _OnReaderType
Task DataHandler()
{
//Recieving-Data and Stuff
_OnSerialNumber(this, new OnReaderCommonEventArgs { SerialNumber = RFIDParser.ParseSerialNumber(data) });
_OnReaderType(this, new OnReaderCommonEventArgs { ReaderType = RFIDParser.ParseReaderType(data) });
}
}
And in the Main-Class, which will be used by the user. So the user can only subscribe to the event from this class-object:
public partial class PUR_100U
{
public delegate void EventHandler(object sender, OnReaderCommonEventArgs e);
public event EventHandler OnSerialNumber;
public event EventHandler OnReaderType;
public PUR_100U(int portnumber)
{
dataTransfer = new DataTransfer(portnumber, GetIdentifierList());
dataTransfer._OnSerialNumber += dataTransfer__OnSerialNumber;
dataTransfer._OnReaderType += dataTransfer__OnReaderType;
}
void dataTransfer__OnSerialNumber(object sender, OnReaderCommonEventArgs e)
{
if (OnSerialNumber != null) { OnSerialNumber(this, new OnReaderCommonEventArgs { SerialNumber = e.SerialNumber }); }
}
void dataTransfer__OnReaderType(object sender, OnReaderCommonEventArgs e)
{
if (OnReaderType != null) { OnReaderType(this, new OnReaderCommonEventArgs { ReaderType = e.ReaderType }); }
}
}
Example of user-usage:
rfid = new PUR_100U(20);
rfid.OnSerialNumber += rfid_OnSerialNumber;
rfid.OnReaderType += rfid_OnReaderType;
Is there a better way of doing this?
I need to Raise an Event from another Class - i know that this is not possible - but I need a workaround for this.
That is rather trivial:
class Foo
{
public event EventHandler Fooed; //note, name is not OnFoo
public void FireFooed() => Fooed?.Invoke(this, new EventArgs);
}
And now, fire the event at will:
var foo = new Foo();
foo.FireFooed();
The question is, why do you want to do this? It seems like a really bad idea. Fooed should fire only and only if the preconditions inside Foo for it to fire are met; if you need Fooed to fire, then make the preconditions happen!
Firing Fooed at will if the conditions aren't met will break all other listeners, don't do that.
I have 'BasePage' class which is base class for all other pages in my project.
In initialization, I'm adding EventHandler for 'SystemNavigationManager' for event 'BackRequest'. For some reason that line id causing 'AccessViolationException' when XAML designer is trying to render XAML of class that extends 'BasePage'
I'm not familiar with UWP, so I'll be very grateful for tips.
BasePage
public class BasePage: Page {
internal string title = "";
internal HeaderView headerView;
public BasePage() {
this.Loaded += BasePage_Loaded;
// FIXME: For some reason if this line is uncommented then xaml designer fails.
SystemNavigationManager.GetForCurrentView().BackRequested += BasePage_BackRequested;
}
private void BasePage_BackRequested(object sender, BackRequestedEventArgs e) {
bool handled = e.Handled;
this.BackRequested(ref handled);
e.Handled = handled;
}
private void BackRequested(ref bool handled) {
//Get a hold of the current frame so that we can inspect the app back stack.
if (this.Frame == null)
return;
// Check to see if this is the top-most page on the app back stack.
if (this.Frame.CanGoBack && !handled) {
// If not, set the event to handled and go back to the previous page in the app.
handled = true;
this.Frame.GoBack();
}
}
private void setupPageAnimation() {
TransitionCollection collection = new TransitionCollection();
NavigationThemeTransition theme = new NavigationThemeTransition();
var info = new ContinuumNavigationTransitionInfo();
theme.DefaultNavigationTransitionInfo = info;
collection.Add(theme);
this.Transitions = collection;
}
private void BasePage_Loaded(object sender, Windows.UI.Xaml.RoutedEventArgs e) {
setupPageAnimation();
}
}
SOLUTION
Just like Ivan said, final code looks like this. Without of a trace of bug.
BasePage
public BasePage() {
this.Loaded += BasePage_Loaded;
}
protected override void OnNavigatedTo(NavigationEventArgs e) {
base.OnNavigatedTo(e);
SystemNavigationManager.GetForCurrentView().BackRequested += BasePage_BackRequested;
}
protected override void OnNavigatedFrom(NavigationEventArgs e) {
base.OnNavigatedFrom(e);
SystemNavigationManager.GetForCurrentView().BackRequested -= BasePage_BackRequested;
}
You shouldn't subscribe to back events on constructor but OnNavigatedTo and unsubscribe in OnNavigatedFrom. Even if it didn't crash it would cause a lot of problems because your back logic would be activated on all previous pages when you press the back button.
I have a custom checkbox control that inherited from System.Windows.Forms.Control
and it hasn't CheckedChanged event. I want to implement CheckedChange same as dot net native CheckBox. How can I do it well ?
You are inheriting fromn Control, not CheckBox, so the solution is similar to the one proposed by Frigik, but it's not exactly that one.
First of all you have to define the event in your class, i.e.:
public event EventHandler CheckedChanged;
In this way every developer using your control can subscribe/unsubscribe to the event. This is not enough, since the event will never be triggered. To do so, you have to define a method to trigger it, and the call this method whenever the state of your control changes:
private void RaiseCheckedChanged()
{
if (CheckedChanged!= null)
CheckedChanged(this, EventArgs.Empty);
}
Where this method will be called depends on the structure of your control. For instance if you have a property Checked, you could call the method in its setter:
public bool Checked
{
get { return _checked; }
set
{
_checked = value;
RaiseCheckedChanged();
}
}
Try this code :
CheckBox chkList1 = new CheckBox();
chkList1.CheckedChanged += new EventHandler(CheckBox_CheckedChanged);
protected void CheckBox_CheckedChanged(object sender, EventArgs e)
{
// Do your stuff
}
Try this:
public class YourCheckBox:CheckBox
{
public event EventHandler<EventArgs> OnCheckedChangedCustom;
protected override void OnCheckedChanged(EventArgs e)
{
if (OnCheckedChangedCustom!=null)
{
OnCheckedChangedCustom(this, EventArgs.Empty);
}
base.OnCheckedChanged(e);
}
}
I have a custom control in C# WinForms called BaseControl and there I have a property called Selected.
I want to have an event SelectedChanged and virtual method OnSelecteChanged in the base control and they should behave in the same manner as we have in Control class for many properties i.e. Click event and OnClick method.
Means anyone who derives from my BaseControl can either bind to the event or can override the OnSelectedChanged method.
So, when the value of Selected property is changed event should be fired and if the method is overridden control should go to that method.
I know how to fire the event but don't know how to do it for method.
Please guide me...
Below is an example of how events should be implemented:
public class BaseControl : Control
{
private object _selected;
public object Selected
{
get { return _selected; }
set
{
if (!Equals(_selected, value))
{
_selected = value;
OnSelectedChanged(EventArgs.Empty);
}
}
}
public event EventHandler SelectedChanged;
protected virtual void OnSelectedChanged(EventArgs e)
{
if (SelectedChanged != null)
SelectedChanged(this, e);
}
}
With this example, you can override OnSelectedChanged in an overriden class, like this:
public class MyControl : BaseControl
{
protected override void OnSelectedChanged(EventArgs e)
{
base.OnSelectedChanged(e);
// My own logic.
}
}
private bool _selected;
public bool Selected
{
get { return _selected; }
set
{
if (value != _selected)
{
_selected = value;
OnSelectedChanged();
}
}
}
public event EventHandler SelectedChanged;
protected virtual void OnSelectedChanged()
{
var handler = SelectedChanged;
if (handler != null)
handler(this, EventArgs.Empty);
}
Basically you don't fire the event from your Selected property setter - you call the method, and make the method call the event. Anyone overriding the method should call base.OnSelectedChanged to make sure the event still fires. So your method should look something like this:
protected virtual void OnSelectedChanged(EventArgs e) {
EventHandler handler = Selected; // Or your own delegate variable
if (handler != null) {
handler(this, e);
}
}