Develop Reference

How to make textbox appear only after user clicks button in c#

How would I make a textbox appear only after clicking a button. THis means that It should be hidden, and once user clicks, then it can appear.
private void button7_Click(object sender, EventArgs e)
{
// .. what next?
}

You can use Control.Visible to make any control visible or hidden:
private void button7_Click(object sender, EventArgs e)
{
theTextBox.Visible = true;
}
Just set it's Visible property to false initially (ie: in the designer).

Assuming you have defined a TextBox textBox1 somewhere:
private void button7_Click(object sender, EventArgs e)
{
textBox1.Visible = !textBox1.Visible;
}
This way you can toggle the visibility.
You can set it just to true if you like, but make sure the initial Visible state, you can set it in the designer, is false.

How to make a textbox invisible when radio button checked

I am working on C# application. I have 10 radio buttons in a group panel, so now if I only checked the radioButton10 then textBox1 will be visible, if I checked someone of the other radio Buttons (radioButton1 .... radioButton9) then textBox1 should be invisible.
I wrote the following code but the textBox1 is still visible. If the code is right where can I wrote it(form load, some function ... etc) if it's NOT, then Please Help.
public TeamInfoForm()
{
InitializeComponent();
showTeam();
if (radioButton10 .Checked)
textBox1 .Visible = true;
else
textBox1 .Visible = false;
}

I think you forgot to implement the event that occur when you check or uncheck the radiobutton. Try to imlpement "OnCheckChanged" event for the radiobutton and you have to set autopostback to true if you want that the event occurs, otherwise the event won't work.

Initially you have to set the Visible property of textBox1 to false in Forms Designer. Otherwise you can set it in FormInitialize() method. Next you have write code like below
public void ToggleTextBox()
{
textBox1.Visible = radioButton3.Checked;
}
private void radioButton1_CheckedChanged(object sender, EventArgs e)
{
ToggleTextBox();
}
private void radioButton2_CheckedChanged(object sender, EventArgs e)
{
ToggleTextBox();
}
private void radioButton3_CheckedChanged(object sender, EventArgs e)
{
ToggleTextBox();
}

How to prevent radio button change status

I am trying to prevent the change status of textbox and radio button when the button (btactive) is clicked. I can use property IsReadOnly for textbox but I can not find this property in radio button, Is there anyway to prevent the change status of radiobutton ?
Here is my code :
private void btActive_Click(object sender, RoutedEventArgs e)
{
if (check != 0)
{
udhour.IsReadOnly = true;
udmin.IsReadOnly = true;
testvalue.IsReadOnly = true;
//How can I set Isreadonly for radio button
}
}

Disable radio button. use IsEnabled=false

Change the AutoCheck property of the RadioButton to False

Add radiobutton.IsEnabled = false in the code.

Write and Checked changed event for the readonly effect.
void radioButton1_CheckedChanged(object sender, EventArgs e)
{
radioButton1.Checked = !radioButton1.Checked;
}

Radio button checked changed event fires twice

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

selected item change ComboBox

Is there any way to prevent changing the selected item in a ComboBox only if for certain conditions? I want to allow update the selected item's displayValue in the ComboBox. But I don't want user to change the selected item when it's being updated. This is a windows application.

Inside your class:
private int _selectedIndex = 0;
Inside your form load method:
comboBox1.Enter += new EventHandler(comboBox1_Enter);
comboBox1.SelectedIndexChanged += new EventHandler(comboBox1_SelectedIndexChanged);
Then the rest of the code:
protected void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {
if (true) { // Add your validation or certain condition here.
(sender as ComboBox).SelectedIndex = _selectedIndex;
}
}
protected void comboBox1_Enter(object sender, EventArgs e) {
_selectedIndex = (sender as ComboBox).SelectedIndex;
}

Try setting set the Enabled property to false. (Or some third-party toolkits like Telerik have a ComboBox with a ReadOnly property.)