I have a winforms program containing a RichTextBox.
The user inputs the text into the RichTextBox.
I wish to receive the input through keyboard events and not through textBox1.Text property, validate the string and only display it in the RichTextBox later.
How can I prevent the RichTextBox from displaying the input text by the user, even though the user inputs the text into the RichTextBox?
The RichTextBox is selected and has focus.
I am sorry. I just wanted to simplify the issue and therefore I neglected to mention that it is not a TextBox but a RichTextBox. It turns out that it matters, as the proposed solution is based on the PassowrdChar property, which is not natively supported by RichTextBox. I do not wish to create an inherited class for a property which is not even being used as such, only to suppress displaying the user input at input time.
You can actually use the KeyDown event. By doing that, you have an ability to validate the user input.
Tutorial
private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
//
// Detect the KeyEventArg's key enumerated constant.
//
if (e.KeyCode == Keys.Enter)
{
MessageBox.Show("You pressed enter! Good job!");
}
else if (e.KeyCode == Keys.Escape)
{
MessageBox.Show("You pressed escape! What's wrong?");
}
}
With that said, you have to store user input in string variable, validate it through the event and only then set variable value in textbox.
You can use this:
private void richTextBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char c = e.KeyChar;
// ..
// handle the character as needed
// ..
e.Handled = true; // suppress the RTB from receiving it
}
Note that you may or may not want to treat mouse events like right mouseclicks to control inserting via the mouse..
Related
I have already checked other questions here but the answers are not related to my issue. the following code allows textbox1 to only accept numbers if the physical keyboard (laptop) is pressed:
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char ch = e.KeyChar;
if ( !char.IsDigit(ch))
{
e.Handled = true;
}
}
but this is not what I wanted (I dont use physical laptop keyboard).
As shown in screenshot, I have windows form with buttons and a textbox. I designed this keyboard and it works well but I want textbox1 to only accept numbers and the ".".
There are only two lines of code inside each button (and only code in the project) which is:
private void buttonName_Click(object sender, EventArgs e)
{
// each button only has this code.
textBox1.Focus();
SendKeys.Send(buttonName.Text);
}
I know how to set txtbox to accept numbers if the physical (laptop ) keys are pressed but here in this case I have control buttons in windwos form and I want to set textBox1 to only accept numbers and the ".". Please help in how to achieve this. Thank you
Declare a string variable at form level, use it to store the last valid text and to restore it when an invalid text is entered on the TextChanged event of your textbox.
string previousText;
public Form1()
{
InitializeComponent();
previousText = String.Empty;
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
int dummy, changeLenght, position;
if (!String.IsNullOrWhiteSpace(textBox1.Text) && !int.TryParse(textBox1.Text, out dummy))
{
position = textBox1.SelectionStart;
changeLenght = textBox1.TextLength - previousText.Length;
textBox1.Text = previousText;
textBox1.SelectionStart = position - changeLenght;
}
else
{
previousText = textBox1.Text;
}
}
position and changeLenght are used to keep the cursor where it was before restoring the text.
In case you want to accept numbers with decimals or something bigger than 2147483647, just change dummy to double and use double.TryParse instead of int.TryParse.
private void textBox1_TextChanged(object sender, EventArgs e)
{
int changeLenght, position;
double dummy;
if (!String.IsNullOrWhiteSpace(textBox1.Text) && !double.TryParse(textBox1.Text, out dummy))
{
...
}
}
Suppose button1 is your button control, you could do this:
private void allButtons_Click(object sender, EventArgs e)
{
Button btn = sender as Button;
char c = btn.Text[0]; //assuming all buttons have exactly 1 character
if(Char.IsDigit(c) || c == '.')
{
//process
textBox1.Focus();
SendKeys.Send(btn.Text);
}
//otherwise don't
}
I'm assuming you put this in a common handler, to which you already wired all your buttons (i.e. allButtons_Click).
Problem with this approach, it allows you to type values like 0.0.1, which are most likely invalid in your context. Another way to handle this is to process TextChanged event, store previous value, and if new value is invalid, restore the old one. Unfortunately, TextBox class does not have TextChanging event, which could be a cleaner option.
The benefit of you determining the invalid value is modularity. For example, if you later decide your user can enter any value, but only numbers can pass validation, you could move your check from TextChanged to Validate button click or similar.
Why users may want that - suppose one of the options for input is copy/paste - they want to paste invalid data and edit it to become valid, for example abc123.5. If you limit them at the entry, this value will not be there at all, so they now need to manually paste into Notepad, cut out in the invalid characters, and paste again, which goes against productivity.
Generally, before implementing any user interface limitation, read "I won't allow my user to...", think well, whether it's justified enough. More often than not, you don't need to limit the user, even for the good purpose of keeping your DB valid etc. If possible, never put a concrete wall in front of them, you just need to guide them correctly through your workflow. You want users on your side, not against you.
I have a form where a user enters a 4 digit pin number. When the pin number is entered, I would like to call my method automatically once the last number of the pin number is pressed. I am assuming this needs to be done in a keydown event on the textbox.
Here is what I tried so far.
private void txtPinNumber_KeyDown(object sender, KeyEventArgs e)
{
if (txtPinNumber.Text.Trim().Length == 4)
{
SendKeys.Send("{ENTER}");
if (e.KeyCode == Keys.Enter)
Verify_Pin();
}
}
It seems to work but the user has to press an addition key to execute the method. What am I missing?
There's no reason to press Enter programmatically and then check for it. Just call the other method.
Also, the KeyDown event fires before the Text property changes to reflect the most recently typed character, so you'll have to place that code in a different event.
Use TextChanged or KeyUp.
private void txtPinNumber_TextChanged(object sender, KeyEventArgs e)
{
if (txtPinNumber.Text.Trim().Length == 4)
Verify_Pin();
}
You said
When the pin number is entered, I would like to call my method automatically once the last number of the pin number is pressed.
So you can simply do this in the KeyUp event of your textbox
private void txtPinNumber_KeyUp(object sender, KeyEventArgs e)
{
if (txtPinNumber.Text.Trim().Length == 4)
Verify_Pin();
}
BTW, it is advisable to let user press enter and then you run the code. Because it can be that user accidentally presses the last number wrong.
I'm writing a desktop app in win forms using C#.I use the following code to convert my textbox to numeric textboxes :
private void txtPrice_KeyPress(object sender, KeyPressEventArgs e)
{
//if (!char.IsControl(e.KeyChar)
// && !char.IsDigit(e.KeyChar)
// && e.KeyChar != '.')
// {
// e.Handled = true;
// }
if(!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}
is it ant design pattern or technique to write above code only once, and dont write it , each time for every textbox in the form?
Subclass the TextBox class, add your numeric checking to it, and use the new text box in place of the usual one.
Example
How to: Create a Numeric Text Box
Create a new component called numeric textbox that inherits TextBoxBase class.
Your code you wrote here won't work because someone can copy and paste text values.
You have to override text_change event for that.
If you want customisation, Robert's answer is the best way to go. Alternatively, in case you're not aware of it, you could use the NumericUpDown control which is built in.
create a method....for example
private void press(object sender, KeyPressEventArgs e)
{
//what ever code here,,,,,,i dont care
}
//i am assuming you are using visual studio.net
//highlight or select your text boxes or text box....
//then go to properties window ,,,,,
//after that click on the lightening icon....or events icon
//then go to your KeyPress event------- and click the drop down button
//after that Add the Method you want to be implemented by the Control.......
Is it possible to restrict user input to DataGridView cell by means of RegEx? For example set format of cell input to something like this [0-9]{2} to forbid user enter something except 2 digits.
UPDATE
Sorry, I was not very clear. I'm aware about CellValidation event and that I can check entered value after user input. But I wonder if I can prevent wrong user input before this event. I mean that user cannot input letters when cell regex is [0-9]. Is is possible?
If you want to prevent invalid values as they're typed, you can handle the EditingControl.KeyPress event. Sample code below. You have to modify your regular expressions to allow incomplete values, though. And you should still use proper validation, because there are other ways to get data into the grid (such as copy paste).
private string pattern = "^[0-9]{0,2}$";
private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
dataGridView1.EditingControl.KeyPress -= EditingControl_KeyPress;
dataGridView1.EditingControl.KeyPress += EditingControl_KeyPress;
}
private void EditingControl_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsControl(e.KeyChar))
{
Control editingControl = (Control)sender;
if (!Regex.IsMatch(editingControl.Text + e.KeyChar, pattern))
e.Handled = true;
}
}
#Ginosaji , your code is good but with editingControl.Text + e.KeyChar you're assuming that user enters the last char at the end of the control text. What if the user places the char in the middle of the control somewhere?
I have implemented validation rules on a textBox in my WinForm and it works well. However it checks the validation only when I tab out of the field. I would like it to check as soon as anything is entered in the box and everytime the content changes. Also I'd like it to check validation as soon as the WinForm opens.
I remember doing this fairly recently by setting some events and whatnot, but I can't seem to remember how.
If you're using databinding, go to the Properties of the textbox. Open (DataBindings) at the top, click on the (Advanced) property, three dots will appear (...) Click on those. The advanced data binding screen appears. For each property of the TextBox that is bound, in your case Text, you can set when the databinding, and thus the validation, should "kick in" using the combobox Data Source Update mode. If you set it to OnPropertyChanged, it will re-evaluate as you type (the default is OnValidation which only updates as you tab).
TextChanged event
in the future you can find all of the events on the MSDN library, here's the TextBox class reference:
http://msdn.microsoft.com/en-us/library/system.windows.forms.textbox(VS.80).aspx
How will your data be valid if it isn't finished? i.e. a user types a number and you try and validate it as a date?
When binding your textbox to a bindingSource go to Advanced and select validation type
"On Property Changed". This will propagate your data to your entity on each key press.
Here is the screen shot
You should be checking on KeyPress or KeyDown events and not just your TextChanged event.
Here is a C# Example direct from the MSDN documentation:
// Boolean flag used to determine when a character other than a number is entered.
private bool nonNumberEntered = false;
// Handle the KeyDown event to determine the type of character entered into the control.
private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
// Initialize the flag to false.
nonNumberEntered = false;
// Determine whether the keystroke is a number from the top of the keyboard.
if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
{
// Determine whether the keystroke is a number from the keypad.
if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
{
// Determine whether the keystroke is a backspace.
if(e.KeyCode != Keys.Back)
{
// A non-numerical keystroke was pressed.
// Set the flag to true and evaluate in KeyPress event.
nonNumberEntered = true;
}
}
}
//If shift key was pressed, it's not a number.
if (Control.ModifierKeys == Keys.Shift) {
nonNumberEntered = true;
}
}
// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
// Check for the flag being set in the KeyDown event.
if (nonNumberEntered == true)
{
// Stop the character from being entered into the control since it is non-numerical.
e.Handled = true;
}
}