Develop Reference

how to use TextBox_Textchanged event with Regex for RequiredField Control

the textbox is associated with two RequiredFiled validators
also this textbox has TextChanged event.
I would like to allow first execute RequiredFiled validators then execute Textchanged event.
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
if (!System.Text.RegularExpressions.Regex.IsMatch(TextBox1.Text,Regular_Expression))
{
Label2.Text = "from textChanged.";
}
}
if (!System.Text.RegularExpressions.Regex.IsMatch(TextBox1.Text,Regular_Expression))
here how to use regular expression with (requiedfiled, regularExpression controls)?
Can someone help me how to use RequiredFiled controls with text-box?
Actually, this script is for first validate required filed controls then execute textbox_Textchanged event. because the movement when the filled value in textbox, textbox change event is firing, so OOB(out of the box) control is not executing properly. to execute textbox required filed OOB control if the value is valid then textbox_TextChanged event should execute. just googled and find the
Regex.IsMatch(textbox,RegularExepression) but don't know how to use Regular
Expressions.

I want method to run (event to occur) while i am typing something in textbox

I want method to run (event to occur) while i am typing something in textbox ( i dont want to click button) for example i have a a textbox and a listbox in a same form and while i am writing text in textbox it should simultaneously print that in listbox without clicking an button

use Text Changed event for your textbox
Text Changed event

Utilize the TextBox control's TextChanged event.
This event is raised if the Text property is changed by either a programmatic modification or user interaction.
For more information about handling events, see Handling and Raising Events.
You can access it through the properties list, or you can create it at Initialize or Form_Load or even in the Form constructor using:
textBox1.TextChanged += textBox1_TextChanged;
private void textBox1_TextChanged(object sender, EventArgs e) { }

Winform Checkbox MouseDown event handler not allowing CheckedChanged event to fire

I have a WinForm which contains a multitude of controls interdependent on each other for their visibility and content.
I have a pair of radio buttons, controlling a combobox's (ComboBoxA) enable/disable flag and content. The selection on this combobox controls the visibility of a checkbox. The checking of this checkbox controls another combobox's (ComboBoxB) visibility and content. Business requirements are quite complicated around these controls. As a result, I require the ability to fire of the events programmatically and through user action, doing different things in each case.
In the checkbox's case, I check it programmatically while loading data (if needed), which fires the CheckedChanged event which in turn does additional action controlling ComboBoxB. The code for this is pretty vanilla, nothing special, but my question is more theoretical than practical. Please keep reading.
Due to this requirement, I need a way to distinguish between programmatic checking and user action. I tried using the Click event and CheckedChanged event, setting a flag in the click event, signifying user action. Unfortunately, the CheckedChanged event fires before the Click event, dead-ending this trick.
Now, I tried using the MouseDown event to capture user action. But funnily enough, once the event fires, checkbox remains unchecked and the CheckedChanged event doesnt fire.
Now, I have managed to use a flag in the code to determine programmatic checking and use that to distinguish between the two, but I was curious as to why the MouseDown event didnt allow the checkbox to be checked. Any ideas? I searched online but either I didnt do a thorough job of it, or google is not returning the right results for me. I apologize if anybody is actually able to find a google result for this problem.

It's something else in your code, not the MouseDown event that's preventing the CheckChanged to be fired.
Here is how I know this:
I've added a checkbox and a button to an empty form, and added event handlers to Click on the button, and on the checkbox CheckedChanged, KeyDown and MouseDown events. I've also added to the form a string variable called LastEventRaised, and in the CheckedChanged I've simply shown a MessageBox:
string LastEventRaised = string.Empty;
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
MessageBox.Show("Checked changed " + LastEventRaised);
LastEventRaised = string.Empty;
}
private void checkBox1_KeyDown(object sender, KeyEventArgs e)
{
LastEventRaised = "KeyDown";
}
private void checkBox1_MouseDown(object sender, MouseEventArgs e)
{
LastEventRaised = "MouseDown";
}
private void button1_Click(object sender, EventArgs e)
{
LastEventRaised = "programmatically";
checkBox1.Checked = !checkBox1.Checked;
}
Each time the message box popped up I've got the correct message.

Onclick event for textbox in csharp form application

I'm creating form application on c# . I have dragged a textbox with some text in it.
private void textBox1_Click(object sender, EventArgs e)
{
}
Now what is the event for the onlick on textBox1 ?
I need to add this on that function textBox1.Clear();
P.S I searched everywhere. But all i can find is jquery and javascripts... No c#.
EDIT
I tried onfocus like below..but its not working
private void textBox1_OnFocus(object sender, EventArgs e)
{
MessageBox.Show("dsd");
}

If you want to do something when the control is clicked the handle the Click event, not the TextChanged event. Presumably you just double-clicked the control in the designer. That will only handle the default event. To handle other events, open the Properties window, click the Events button at the top and then double-click the appropriate event.
That said, is Click really appropriate? What if the user enters the TextBox using the Tab key? If what you actually want to do is act when the control gets focus then you should handle the Enter event.

You can handle OnFocus/GotGocus event in the TextBox, and clear the text in the textbox.
Hope this helps.

Equivalent of WinForms TextBox.Validating event in WPF

In WinForms I could handle the Validated event to do something after the user changed text in a TextBox. Unlike TextChanged, Validated didn't fire for every character change; it only fired when the user was done.
Is there anything in WPF I can use to get the same result, an event raised only after the user is done changing the text?

LostFocus will fire when the user moves from your textbox onto any other control.

It seems that there is no native solution.
The LostFocus event is a good idea. But when the user click on Enter, he wants the TextBox to validate the change.
So here is my suggestion : use the LostFocus event and the KeyDown event when the key is Enter.
private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
// code to lauch after validation
}
private void TextBox_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Enter)
{
// call the LostFocus event to validate the TextBox
((TextBox)sender).RaiseEvent(new RoutedEventArgs(TextBox.LostFocusEvent));
}
}

LostFocus is not equivalent to Validate. It creates lots of problem when you have multiple text boxes on one screen and every text box has some logic written in Validate. In validate event you can control focus easily but not in LostFocus so easily.

You can also try Binding.ValidationRules
Documented at : http://msdn.microsoft.com/en-us/library/system.windows.data.binding.validationrules.aspx
Here is the article to get started:
How to implement binding validations :
http://msdn.microsoft.com/en-us/library/ms753962.aspx