I have some radio buttons on a form. When a user changes the radio button selection, I update another object with that info. Each of the radio buttons has a different event handler, but all of them are for the CheckedChanged event.
Which event is fired first? The CheckedChanged from the radio button that is losing selection, or the CheckedChanged from the radio button that is being selected? Or is it a race?
It takes one minute to create a new WinForms project, drag two radiobuttons on it and assigning two separate event handlers to their CheckedChanged events. So the answer is, in this case: uncheck fires first.
However, it is not documented, so it could change with any .NET update (unlikely, but still). Don't bind your application logic to it.
If you could explain your actual problem, your question can be answered more specifically. I guess your code looks something like this:
private void radioButton1_CheckedChanged(object sender, EventArgs e)
{
SomeLabel.Text = "Option 1";
}
private void radioButton2_CheckedChanged(object sender, EventArgs e)
{
SomeLabel.Text = "Option 2";
}
Change it to take in account the state of the radiobutton:
if ((sender as RadioButton).Checked)
{
SomeLabel.Text = "Option 1";
}
So your code doesn't depend on the order of the events anymore and doesn't execute when it's actually not required.
Related
I'm programming in WinForms.
I have a ComboBox set with an initial gray ForeColor. My goal is to change the text color of this ComboBox when the user start to type something.
I tried to use _TextChanged and TextUpdate Events but don't work.
private void ComboBox1_TextChanged(Object sender, EventArgs e)
{
ComboBox1.ForeColor = SystemColors.ControlText;
}
I already used the Event _SelectedIndexChanged to change the text color when the user select an item from the drop-down list, and it works well, but the text remains gray if the user types something (there is an AutoCompleteCustomSource collection associated to the ComboBox so the user can write instead to use the drop-down list).
Any suggestion?
EDIT
I have solved this way:
Registering in Form1.Designer.cs:
this.ComboBox1.KeyUp += new System.Windows.Forms.KeyEventHandler(this.ComboBox1_KeyUp);`
Using this code:
private void ComboBox1_KeyUp(Object sender, KeyEventArgs e)
{
ComboBox1.ForeColor = SystemColors.ControlText;
}
Use KeyUp, KeyDown, or KeyPress events fired by the textbox. You probably don't want KeyPress for this purpose. TextChanged fires when the text has already been changed, which is why the new character being typed doesn't have a different color when you subscribe to it.
Have you looked at KeyUp event? MSDN Keyup
You should be able to subscribe to this event and do whatever you want inside it.
When I usually work with checkboxes, I check to see if the box is checked with the code below:
if (checkBox1.Checked)
{
Label1.BackColor = Color.Red;
}
This code is usually attached to a button that sets into motion when it's clicked by the user. This time, however, I want to do something, like change the color of a label, the very SECOND the checkbox is checked by the user. That is, I don't want to wait until the user pushes some other button to check if the checkbox is checked in order for the label's color to change.
How do I do this?
Sounds like you need a CheckedChanged event handler. That one's for ASP.Net, but there's a version for winforms as well (and xaml, and so on.)
Then you have to write code inside CheckedChanged Event of checkBox as below:
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (checkBox1.Checked)
label1.ForeColor = Color.Red;
}
Why don't you hook up to the CheckChanged event and implement your ideas there?
My small windows form application has two radio buttons, and initially neither is checked. Until one of them is checked, the "Go" button should be disabled.
I found a very simple way to obtain this, but I'm not sure if I'm setting myself up for a random crash.
I added a timer component, enabled it, and in the Tick event:
private void timer1_Tick(object sender, EventArgs e)
{
bool canGo = (_usRadioButton.Checked || _intlRadioButton.Checked);
if (_goButton.Enabled != canGo)
{
_goButton.Enabled = canGo;
}
}
I know there are other ways to do this, I'm just curious if this way is valid or if I'm going to have an end user throwing exceptions when the timer is firing at the same time the form is updating the Checked property on one of the checkboxes?
If I understood you correctly, you already know about the CheckedChanged event, and are only asking about conflicts in your code. So:
As far as I know it's not multithreading, and there's no danger. The Tick event will actually not fire at the same time the computer is updating the Checked state.
If you place traces in Form.Load and Timer.Tick:
private void Form_Load(object sender, EventArgs e)
{
Console.WriteLine("Form_Load/Thread.CurrentThread.ManagedThreadId=" + Thread.CurrentThread.ManagedThreadId);
}
private void timer1_Tick(object sender, EventArgs e)
{
Console.WriteLine("timer1_Tick/Thread.CurrentThread.ManagedThreadId=" + Thread.CurrentThread.ManagedThreadId);
}
The results show:
Form_Load/Thread.CurrentThread.ManagedThreadId=9
timer1_Tick/Thread.CurrentThread.ManagedThreadId=9
A better solution is to subscribed to the CheckedChanged event of your radio buttons and then enable the "Go" button in that event handler.
This will solve any timing problems you will encounter with this approach.
I'm not certain that it's safer, but you could also subscribe to the CheckedChanged event and use that handler code to enable the Go button. This would save you a timer that would have to run indefinitely.
This is what I'm doing and it results in a stack overflow because it just switches back and forth forever.
private void radioButtonA_CheckedChanged(object sender, EventArgs e)
{
radioButtonB.Checked = !radioButtonB.Checked;
}
private void radioButtonB_CheckedChanged(object sender, EventArgs e)
{
radioButtonA.Checked = !radioButtonA.Checked;
}
There has to be a better way to do this...
try commenting out all of your code and see if it works the way you want.
you don't have to uncheck the other radio buttons in code
Is it toggling of "One" radio button what you were trying to do? If so, I tried this, and it works for me:
Set the Radio Button AutoCheck property to FALSE.
Create a "Click" event for the Radio Button.
In the Click Event Handler for the Radio Button paste the code:
radioButton.Checked = !radioButton.Checked;
I hope this helps.
You can disable the Event in the code before changing the Checked value, then add it again immediately afterwards.
In Visual C# Form Application, When I Click on the button I want to add to the other controls(like listboxes,labels,textboxes) in same form.
How do I do this?
I have no idea what "to come to the other controls" might mean. But the event handlers in your Form derived class is the switchboard. Implement the button's Click event and have it do whatever you want done with any other controls. A trivial example:
private void button1_Click(object sender, EventArgs e) {
label1.Text = "You clicked the button!";
}
In the form designer, add an event handler to the button's Click event.
The form designer will give you a new method like this; add your code into this method:
private void button_Click(object sender, EventArgs e)
{
// Write some code that uses list boxes, labels, text boxes etc.
}
You question is somewhat unclear, but if you simply want to access other controls on the form, just go ahead and do so:
private void YourButton_Click(object sender, EventArgs e)
{
string someValue = yourTextBox.Text;
// do something with the value
}
If you want to add one event handler to many controls, you can do it.
Just go to properties of control you wish to subscribe, find appropriate event from list (ex: onClick) and choise your existed handler.
But this method will be sutable if events compotable.
Describe your task more detail.