Develop Reference

CheckBox (event) method for "checked = false"

Is there any method or Is it possible to write a method to execute a set of instructions when a (Windows Form) checkbox is unchecked (but not when checked)? I will clarify this providing my sample code.
Existing Sample Code:
private void ChkBox_CheckedChanged(object sender, EventArgs e)
{
if (ChkBox.Checked == false)
{
MessageBox.Show("unchecked");
}
}
Q: Could that if condition be avoided by writing a method for this which gets executed only when checkbox is unchecked.
Illustration:
Something like this:
private void ChkBox_Unchecked(object sender, EventArgs e)
{
MessageBox.Show("unchecked");
}
additional comments: I don't have anything to execute for event 'checkbox is checked' .. So just thinking if I can avoid checkchanged event by replacing it with unchecked type of event.

If you really need that strange events, then create custom check box by inheriting from CheckBox. Override it's OnCheckedChanged event, and add your Unchecked event:
public class StrageCheckBox : CheckBox
{
public event EventHandler Unchecked;
protected override void OnCheckedChanged(EventArgs e)
{
base.OnCheckedChanged(e);
if (!Checked)
OnUnchecked(e);
}
protected virtual void OnUnchecked(EventArgs e)
{
if (Unchecked != null)
Unchecked(this, e);
}
}
Use StrangeCheckBoxes instead of default check boxes. Subscribe to Unchecked event. Voila, you have that strange behavior.
Remark Actually I would not suggest usage of custom control or if/else in all scenarios. If you have many checkboxes with this kind of behavior, then custom control is better than many duplicated if/else in each handler. If you have several controls, or single handler for all checkboxes, then I'd go with if/else approach.

You can inherit the CheckBox and override OnCheckedChanged
class ExtendedCheckBox : CheckBox
{
public event EventHandler Unchecked;
protected override void OnCheckedChanged(EventArgs e)
{
base.OnCheckedChanged(e);
if (Checked == false)
OnUnchecked(e);
}
}

No, the only event exposed is one to detect when a change to the state occurred, then you must check the state to determine how it changed.
You could, if so inclined, create your own control which essentially wraps this one and exposes such state-distinguishing events, but this seems entirely pointless.

No, sorry. That's the only event you can trigger for a state change. Your code looks fine.
Any reason you don't like it?

As far as I know the event is fired on all changes, you could write your own control which differentiates the value selected and raises separate events but not sure it is really worthwhile.

I don't think you can do something like this, but if you have many instructions to execute if the checkbox was unchecked and you don't want to encapsulate them in an if statement you could check for checked at the beginning and return:
private void ChkBox_CheckedChanged(object sender, EventArgs e)
{
if (ChkBox.Checked) return;
MessageBox.Show("unchecked");
}

This will be a simple straight forward solution although the best suggested way will be to inherit from the CheckBox and modify the events. But, a relatively simple way is as follows:
Reduce the CheckBox width so that the CheckBox Label is no longer visible. Only the box should be visible. Then, include another label beside the box which should be mutually exclusive from the box.
Now, edit the CheckBox Clicked event. Use some sort of a flag to identify the state of the checkbox. Voila!

C# .net Make checkboxes to behave as a radio button

I have a group box which has some radio buttons. I am trying to implement serialization with the help of a tutorial from Code Project. That tutorial supports serialization of checkboxes and not radio buttons. So i need to make the radio buttons in my app as checkboxes (that is they should be check boxes but work like a radiobutton).
I tried writing code, but what happens is when I find that a particular checkbox is checked and I go to uncheck or vice versa, it triggers that checked_changed event handler and this goes into an infinite loop.
Can someone help me out with this?
Thanks
UPDATE:
After seeing your replies, I would like to say thanks a lot. Yes, You are all right that we should not be messing with the basic properties. I will work with changing the serialization method.
P.S The link for the tutorial is http://www.codeproject.com/KB/dialog/SavingTheStateOfAForm.aspx
Final Update:
After following the replies posted here, I decided not to change the default properties but to change the serializer code. I did that and it now works perfectly. Thanks a lot, everyone.

I agree with all the commenters: do not make checkboxes that act like radio buttons, it flies in the face of UI conventions and confuses users.
The right way to do this is to fix your code to serialize the radio buttons, but without seeing your code it's hard to know how to help you. For a start, you can fix the CheckedChanged looping by temporarily removing the event handler before you do anything. For example:
myCheckBox.CheckedChanged -= MyCheckedChangedEventHandler;
myCheckBox.Checked = true;
myCheckBox.CheckedChanged += MyCheckedChangedEventHandler;
If this alone doesn't fix your issue, please show us your code and we'll try to help more.
Edit: Based on the tutorial listed in your update, I'm guessing the problem happens when you call FormSerialisor.Deserialise(), which triggers your controls' event handlers to fire? If that's the case, the quick fix is to just do what I mentioned: remove the radio button event handlers before calling FormSerialisor.Deserialise() and then re-add them afterwards. Example:
myRadioButton.CheckedChanged -= MyCheckedChangedEventHandler;
FormSerialisor.Deserialise(this, mySerialisepath);
myRadioButton.CheckedChanged += MyCheckedChangedEventHandler;
You may also need to edit the FormSerialisor class to handle RadioButtons; just copy the code that handles checkboxes but change all the references to RadioButton. It's not clear from your question whether this step will be necessary or not.

Like the comments say, you're better of getting serialisation to work with radio buttons than messing around with checkboxes. Having said that, to get the effect you need, just set a variable that indicates you're already handling a change event, and test for it. Something like this (it's terrible code, but demonstrates the idea):
private bool autoChange = false;
private void ChangeHandler() {
if (!autoChange) {
autoChange = true;
/* Do stuff */
autoChange = false;
}
}

Unregister from the Checkedevent (by using -=) before doing that. And re-register after you're done.
(I'm not arguing with the comments. Just answering the question.)

Hello, here a simple ansewer to transform the CheckBox to a RadioButton:
object clickBox = null;
private void checkBox_Click(object sender, EventArgs e)
{
clickBox = sender;
foreach (Control c in this.Controls)
{
if (c is CheckBox)
{
if (c != clickBox)
{
((CheckBox)c).Checked = false;
}
}
}
And add this Click event o every Checkbox
Finish

Take the CheckedListBox and call ItemCheck Event and use below code It will behave like Radio buttons (It works for me):-
private void chkListBox_ItemCheck(object sender, ItemCheckEventArgs e)
{
if (e.NewValue == CheckState.Checked)
{
for (int item = 0; item < chkListBox.Items.Count; item++)
{
chkListBox.SetItemChecked(item, false);
}
}
}

How to clear the value of an Autocomplete Box?

Just like many things in WPF, sometimes the easiest things are the ones that are hardest to find examples for! How do you clear out the current text of an AutoCompleteBox? In my OnFocus event I want to make sure that the user is given a clear box for entry. So my event procedure looks like
private void autGlobal_GotFocus(object sender, RoutedEventArgs e)
{
AutoCompleteBox acb = (AutoCompleteBox)sender;
if (acb.SearchText == "Search Term")
{
//clear out the box if it has the focus
this.autGlobal.Text = "";
}
}
However, setting the text property directly does not seem to work. Am I missing something obvious?

You need reset Selected Item too.
private void SearchAutoCompleteBox_OnPreviewMouseDown(object sender, MouseButtonEventArgs e)
{
SearchAutoCompleteBox.SelectedItem = null;
SearchAutoCompleteBox.Text = string.Empty;
}

Have you tried setting the property on your local variable?
acb.Text = string.Empty;
I have a feeling there may be additional code affecting the .Text field when the focus or textchange events are firing.

I think I found the answer after spending a ton of time on this and the XAML. This code example will not work when the IsTextCompletionEnabled option is set to true in the XAML. I set it to false and this code works fine.

A radio box is automatically checked when the program runs - but it shouldn't be

I'm writing an application in C# using Visual Studio 2010. All of a sudden the strangest thing has started happening, though.
I have two radio boxes at the top of the window, both are set to Checked = False. I have searched everywhere in the code, I see no reason why it would be anything but False.
Now, the first of these two boxes (called Radio1 and Radio2 respectively) has started being automatically checked when the application is executed. This causes a problem since there is an event associated with the boxes being checked, and now this event runs every time the program is opened (resulting in some serious issues).
Has anybody got any ideas why this box is automatically being checked? As I mentioned, I have looked everywhere through the code just in case I had a Radio1.Checked = true; dangling somewhere. But that is not the case.

The RadioButton class contains code to ensure that at least one button in the group is checked when one of them gets the focus and the AutoCheck property is set to True. This implements the standard behavior of radio buttons. If you want non-standard behavior then you have to set their AutoCheck properties to false and implement the checking yourself.

Use a counter mechanism so that you can override the click method the first time. like this
form_load
{
counter=0;
}
private void rb1_Click(object sender, EventArgs e)
{
if (counter == 0) { counter++;}
else {
//Do your stuff
}
}
private void rb2_Click(object sender, EventArgs e)
{
if (counter == 0) { counter++;}
else {
//Do your stuff
}
}
Hope this is helpfull.

There should be no reason for this to happen unless you are setting the property within the designer or via code. Strange.

How to change the behaviour of the DataGridViewComboBoxColumn in C#?

I'm working with a data grid that contains a Combo Box Column, but editing this Combo Box (by simply clicking on it) gets annoying sometimes, since one must click at least twice to change the value of that field. I want to change that behaviour, so I thought it would be very simple: just create a OnMouseOver event to make the mouse-overed combo box be selected, but the only available event is the Disposed one.
Is there any way to change this behaviour?

I just dealt with the same problem, and solved it by setting the DataGridView.EditMode to EditOnEnter.
If you don't like that behaviour for all your other columns, I found this suggestion for placing in the CellEnter event:
if (DataGridView1.Columns[e.ColumnIndex] is DataGridViewComboBoxColumn)
{
((DataGridViewComboBoxEditingControl)DataGridView1.EditingControl).DroppedDown = true;
}
I haven't tried it, but it looks promising. The same technique is discussed on this question.

In Winforms, there's a CellMouseEnter event (and a CellEnter event for non-mouse navigation) on the DataGridView. You can use that to set the selected cell.

The reason you are getting only the Disposed event (I think) is because you are trying to go too deep. I get only the Disposed event when I try to go all the way to dataGridView1.Columns["Column1"]...
Instead, as KeithS mentioned, you can assign the CellMouseEnter event to your DataGridView.
From there, you can do the following...
private void dataGridView1_CellMouseEnter(object sender, DataGridViewCellEventArgs e)
{
if (e.ColumnIndex==0 || e.ColumnIndex==2)
{
dataGridView1.CurrentCell = dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex];
dataGridView1.BeginEdit(true);
}
}
That if-statement is just there to show how to restrict this functionality to certain columns, in case you want that.
The first line inside the if-statement sets the current cell and the second line begins the edit process.
This is a general process that should work with any type of column you can throw into a DataGridView. The DataGridView's EditMode shouldn't matter.

This works really good.
On the CellClick event of the datagridview:
void datagridview1_CellClick(object sender, .Windows.Forms.DataGridViewCellEventArgs e){if (e.ColumnIndex > 0)
{
W1.dGVReports.CurrentCell = W1.dGVReports.Rows[e.RowIndex].Cells[e.ColumnIndex];
W1.dGVReports.BeginEdit(true);
(W1.dGVReports.EditingControl as System.Windows.Forms.DataGridViewComboBoxEditingControl).DroppedDown = true;
}
}