Please read my question its not a duplicate one.
I've three radio buttons on windows form and all these buttons have common 'CheckedChanged' event associated. When I click any of these radio buttons, it triggers the 'CheckedChanged' event twice.
Here is my code:
private void radioButtons_CheckedChanged(object sender, EventArgs e)
{
//My Code
}
I inserted the breakpoint and the whole code within this event iterates twice.
Please tell me why it is behaving like this?
As the other answerers rightly say, the event is fired twice because whenever one RadioButton within a group is checked another will be unchecked - therefore the checked changed event will fire twice.
To only do any work within this event for the RadioButton which has just been selected you can look at the sender object, doing something like this:
void radioButtons_CheckedChanged(object sender, EventArgs e)
{
RadioButton rb = sender as RadioButton;
if (rb != null)
{
if (rb.Checked)
{
// Only one radio button will be checked
Console.WriteLine("Changed: " + rb.Name);
}
}
}
To avoid it, just check if radioButton is checked
for example:
private void radioButton1_CheckedChanged(object sender, EventArgs e)
{
if (radioButton1.Checked)
//your code
}
CheckedChanged is raised whenever the Checked property changes. If you select a RadioButton then the previously selected RadioButton is unchecked (fired CheckedChanged), and then the new RadioButton is checked (fired CheckedChanged).
It's triggering once for the radio button transition from checked to unchecked, and again for the radio button transitioning from unchecked to checked (i.e. any change in checked state triggers the event)
You could set the AutoCheck property true for each RadioButton then catch the Click event instead of the CheckChanged event. This would ensure that only one event is fired, and the logic in the handler can cast the sender to type RadioButton if needed to process the click. Often the cast can be avoided if the handler logic is simple. Here is an example which handles three controls, rbTextNumeric, rbTextFixed and rbTextFromFile:
private void rbText_Click(object sender, EventArgs e)
{
flowLayoutPanelTextNumeric.Enabled = rbTextNumeric.Checked;
txtBoxTextFixed.Enabled = rbTextFixed.Checked;
flowLayoutPanelTextFromFile.Enabled = rbTextFromFile.Checked;
}
{
public partial class Form3 : Form
{
public Form3()
{
InitializeComponent();
}
int click = 0;
private void radioButton1_Click(object sender, EventArgs e)
{
click++;
if (click %2==1)
{
radioButton1.Checked = true;
}
if (click %2==0)
{
radioButton1.Checked = false;
}
if (radioButton1.Checked==true)
{
label1.Text = "Cheked";
}
if (radioButton1.Checked==false)
{
label1.Text = "Uncheked";
}
}
}
}
The other answers are correct but miss the reason for the underlying problem.
When a radio button is checked the first event sent is the change from the unchecked item
however if you check its state by its control name you will still see its old checked status because the form has not been updated yet. To see its true status you need to cast the sender object.
This allows you to perform any actions relating to the condition which is being deselected should you need to do so.
In the not uncommon scenario below multiple radio buttons are sent to the same handler event.
Simply checking the state of the sender for checked will not work here as we need to perform different actions depending on which radio button has been pressed.
So first we ignore any sender that has just been unchecked.
then we identify the checked sender by control name to process the correct action.
private void ModeChangedExample(object sender, EventArgs e)
{
// multiple radio buttons come here
// We only want to process the checked item.
// if you need to something based on the item which was just unchecked don't use this technique.
// The state of the sender has not been updated yet in the form.
// so checking against rdo_A check state will still show it as checked even if it has just been unchecked
// only the sender variable is up to date at this point.
// To prevent processing the item which has just been uncheked
RadioButton RD = sender as RadioButton;
if (RD.Checked == false) return;
if (rdo_A.Name == RD.Name)
{
//Do stuff
}
if (rdo_B..Name == RD.Name)
{
// Do other stuff
}
if (rdo_C.Name == RD.Name)
{
// Do something else
}
}
This problem of double checking happens when there is a series of RadioButton Clicks in succession.I had this same problem.The last click will give two results.To overcome this i made a dummy click in the end.The double click stopped.Try this method.
Venkatraman
Related
I need to check if the RadioButton is checked from the checkchanged event
private void radioButton6_CheckedChanged_2(object sender, EventArgs e)
{
if(radioButton6.Checked)
{
}
}
Is this the properway to do it? Can i access the CheckBox state from the sender object?
Is this the properway to do it?
That depends. If you need each radio button to be very much distinguished. Meaning: You really need to check inside the event method:
if(radioButton6.Checked)
Then this is the way to go. Another case where this can be applied is when you have registered an individual event handler for each radio button. Then you can access the button directly, because in this case the sender will always be e.g. radioButton6.
Can i access the CheckBox state from the sender object?
Yes you can. It might be adviseable in this case: If you decide to register the same method to a bunch of different radio button events then you could use the sender and cast it. This might save you a lot of double code.
private void radioButton6_CheckedChanged_2(object sender, EventArgs e)
{
RadioButton button = sender as RadioButton;
if(button?.Checked == true)
{
}
}
In such a case you can use the Tag property of the RadioButton to distinguish them. Set it in the beginning and then you can check for it.
I have 10 buttons, 0-9 (button0, button1, button2...). When I click any of these buttons, I would like to perform the same routine on them. I would like to know how to, upon clicking of any of these buttons, direct them to the routine below.
private void button0_Click(object sender, EventArgs e)
{
int newValue;
newValue = Convert.ToInt32(Button.text);
}
I have already gone into the properties of each button, then events, and changed the click event to button0_Click (I would have thought this would add "handles button1.click, button2.click, etc." after "private void button0_Click(object sender, EventArgs e)" but if it does that in the background, that's ok as long as it works.)
I also need to know how to identify the button that has been pressed, which is where I'm at with "Convert.ToInt32(Button.text)" (e.g. button2.text = "2").
You can select the same event handler for all the buttons in the designer (in the event tab of the properties window, select the event and there'll be a drop down with all your defined event handlers).
To get which button has been clicked on, cast the sender argument to a Button and you'll have it.
Button button = (Button)sender;
int value = int.Parse( button.Text );
Edit: Also, the "Handles control.event" syntax only exists in Visual Basic.
Edit: Check out the generated code (Form1.Designer.cs, for example) to see how the events are hooked up.
The C# language doesn't use handles to bind events (as VB does). The code for the actual binding is in the generated code for the form, i.e. in the background as you put it.
The sender property is a reference to the control where the event happened. You just need to cast it to the actual type of the control:
private void button0_Click(object sender, EventArgs e)
{
Button button = (Button)sender;
int newValue = Convert.ToInt32(button.text);
}
As an alternative to using the text of the button (for example if you want to translate the application to different languages, or simply don't want to rely on the text), you can put whatever you like in the Tag property of each button, and retrieve it in the event handler.
You could wire them all up to the same event handler an extract the button from sender e.g.
private void button0_Click(object sender, EventArgs e)
{
var button = sender as Button
if (button != null)
{
int newValue = Convert.ToInt32(Button.text);
}
}
I have a windows form with a panel on the left, which consists purely of radiobuttons, and a tabcontrol in the middle, with multiple tab pages within it. Each of these individual tabpages have a series of datagridviews within it, which are shown and hidden depending on which radio button you check.
I accomplish this effect by having each of the radiobuttons on the left assigned a CheckChanged event, which loops through all of the controls within the tabpagecontrol.SelectedTab, and calls .Show() on the corresponding datagridview and calls .Hide() on the rest so that only one datagridview is visible at one time.
My problem occurs when i try to programmatically check one of these RadioButtons. Lets say in Method X, I write RadioButtonA.checked = true. This triggers the usual CheckedChange event handling, which loops through all the datagridviews on the currently selected tabpage and calls .Hide() on everything except the one datagridview form that the radiobutton is supposed to bring up and calls .Show() instead. However, on one of these .Hide() calls on the datagridview, it ends up triggering the RadioButtonA.CheckedChange event AGAIN for a second time. When i look at the sender argument passed to the function, it shows that the sender is the RadioButton i just programmatically clicked on.
I am adding these datagridviews programmatically and can confirm that there are no eventhandlers assigned whatsoever to them. Can anyone help me determine what is causing this additional event to get triggered? Thanks.
For obnoxious change events that trickle through and upset other event handlers on my forms, I've found the only solution is to add a small boolean value:
bool radioIng;
void MyMethod() {
radioIng = true;
try {
radioButton1.Checked = true;
// etc.
} finally {
radioIng = false;
}
}
void radioButton_EventHandler(object sender, EventArgs e) {
if (radioIng) return;
// rest of code here
}
EDIT:
Alternately, you could just remove all of your event handlers and reconnect them later:
void MyMethod() {
try {
radioButton1.CheckChanged -= radioButton_EventHandler;
radioButton2.CheckChanged -= radioButton_EventHandler;
radioButton3.CheckChanged -= radioButton_EventHandler;
// execute your code
radioButton1.Checked = true;
} finally {
radioButton1.CheckedChanged += new EventHandler(radioButton_EventHandler);
radioButton2.CheckedChanged += new EventHandler(radioButton_EventHandler);
radioButton3.CheckedChanged += new EventHandler(radioButton_EventHandler);
}
}
void radioButton_EventHandler(object sender, EventArgs e) {
if (sender == radioButton1) {
// code here to handle
} else if (sender == radioButton2) {
// code here to handle
} else if (sender == radioButton3) {
// code here to handle
}
}
I use checkbox in WPF window. I use some logic in unchecked event of checkbox. And I want to cancel uncheck if need it in the body of this event. How can I do this?
private void chApprove_Checked(object sender, RoutedEventArgs e)
{
btnAddDepartment.IsEnabled = true;
brnRemoveDepartment.IsEnabled = true;
}
private void chApprove_Unchecked(object sender, RoutedEventArgs e)
{
if (lbSource.Count == 0)
{
btnAddDepartment.IsEnabled = false;
brnRemoveDepartment.IsEnabled = false;
}
else
{
MessageBox.Show("Staff already in use! Release it first from dependecies!");
CheckBox myCheckBox = e.Source as CheckBox;
myCheckBox.IsChecked = true;
}
}
Impossible to cancel uncheck !!!
void CheckBox1_Unchecked(object sender, RoutedEventArgs e)
{
if(ResultOfSomeLogic)
{
CheckBox myCheckBox = e.Source as CheckBox;
myCheckBox.IsChecked = True; // Check it again
}
else
{
}
}
Also take a look at EventToCommand Binding Behaviour in MVVM Light to take advantage of CanExecute method.
You could do this easily with an attached behavior (rather than using code behind), you can take a look at this answer if you need a sample of how to structure one (it's only a few lines of code).
My spider-sense is telling me this isn't a very good idea though - I can't imagine a way to "justify" rechecking a checkbox that a user has clicked, it just strikes me as very jarring. Can you not either bind the enabled state of the checkbox to a property on your ViewModel or, if you have an ICommand bound to it, use the CanExecute delegate to enable/disable it based on the same logic?
Bind the IsChecked property of check box. Like
IsChecked="{Binding IsChecked, Mode = TwoWay}"
and in your class define some thing like dis;
private bool isChecked;
public bool IsChecked
{
get
{
return this.isChecked;
}
set
{
this.isChecked = value;
OnPropertyChanged["IsChecked"];
}
}
and in your event
void CheckBox1_Unchecked(object sender, RoutedEventArgs e)
{
if(ResultOfSomeLogic)
{
this.IsChecked = true;
}
else
{
}
}
hope this will work for u..
Good Luck..
In my case, I could not use a solution that allowed unchecking in the first place. If the checked state initiates a critical asynchronous operation, it is not always ideal to uncheck just to check it again: Why allow cancelling this operation if it shouldn't have been allowed to cancel in the first place?
For MenuItems, you can subscribe to the PreviewMouseDown event and set IsCheckable to false; then subscribe to the Click event and set IsCheckable back to true. The reason this works is because IsCheckable just determines whether or not to initiate the state change, unlike IsHitTestEnabled="false" and IsEnabled="False", which will stop all events from firing.
If you try to disable it, no subsequent events will fire making it impossible to restore checkability; by making it uncheckable beforehand, we avoid this mistake. Click also happens to occur after the state would've been changed so it works out quite nicely.
Unfortunately, CheckBox does not have an equivalent IsCheckable property; however, the same concepts described above (i.e., PreviewMouseDown, Click pattern) can produce a similar, if not identical, result.
Well assuming a check box is intended to interact with users instead of programmatic ways, there's a simple way to cancel Unchecked events based on some logic when user hits left mouse button or space bar:
private void CheckBox_PreviewMouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
// If it's already checked so next click would uncheck it hence trigger the Unchecked event.
if ((sender as System.Windows.Controls.CheckBox).IsChecked == true)
{
var isConfirmed = false; // Use your confirmation logic here instead.
// If e.Handled is set to false that will cancel further events such as the Unchecked event.
e.Handled = isConfirmed;
}
}
private void CheckBox_PreviewKeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
// If it's already checked so when user presses space bar it would uncheck it hence trigger the Unchecked event.
if ((sender as System.Windows.Controls.CheckBox).IsChecked == true)
{
if (e.Key == System.Windows.Input.Key.Space)
{
var isConfirmed = false; // Use your confirmation logic here instead.
// If e.Handled is set to false that will cancel further events such as the Unchecked event.
e.Handled = isConfirmed;
}
}
}
I currently determine what page of a tabcontrol was clicked on via the SelectedIndexChanged event.
I would like to detect before the selected index actually changes, for validation purposes. For example, a user clicks a tab page other than the one they are viewing. A dialog is presented if form data is unsaved and asks if it's ok to proceed. If the user clicks no, the user should remain on the current tab.
Currently I have to remember the previous tab page and switch back to it after an answer of 'no.'
I considered MouseDown (and the assorted calculation logic), but I doubt that's the best way.
Add such an event to the tabControl when form_load:
tabControl1.Selecting += new TabControlCancelEventHandler(tabControl1_Selecting);
void tabControl1_Selecting(object sender, TabControlCancelEventArgs e)
{
TabPage current = (sender as TabControl).SelectedTab;
// Validate the current page. To cancel the select, use:
e.Cancel = true;
}
I've actually tried all of the events including the suggestions here and none of the mentioned events occur at the right time to actually trap moving from the tab.
Even the tab page validation event fires when entering the tab rather than leaving it - either that or there's something peculiar going on with my machine or .NET 4. On the other hand, in .NET 4 there is the Deselecting event which fires at the right time for my purposes.
private void tab_Deselecting(object sender, TabControlCancelEventArgs e)
{
}
The TabControl has a collection of TabPages, each of which you can enforce validation on, e.g.:
public partial class MyForm : Form
{
public MyForm()
{
InitializeComponent();
foreach (var page in _tabControl.TabPages.Cast<TabPage>())
{
page.CausesValidation = true;
page.Validating += new CancelEventHandler(OnTabPageValidating);
}
}
void OnTabPageValidating(object sender, CancelEventArgs e)
{
TabPage page = sender as TabPage;
if (page == null)
return;
if (/* some validation fails */)
e.Cancel = true;
}
}