How to make Textbox only accept alphabetic characters

I have a windows forms app with a maskedtextbox control that I want to only accept alphabetic values in.

Ideally, this would behave such that pressing any other keys than alphabetic keys would either produce no result or immediately provide the user with feedback about the invalid character.

---

来自MSDN（这段代码展示了如何处理KeyDown事件来检查输入的字符，在这个例子中它只检查数字输入，你可以修改它以便它可以用于字母输入而不是数字）：

// 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;
    }
}

---

This question has probably been asked and answered a million times on every conceivable programming forum. Every answer provided has the distinction of being unique to the stated requirements.

Since you are using a MaskedTextBox , you have additional validation features available to you and do not really need to handle keypresses. You can simply set the Mask property to something like "L" (character required) or "?" (optional characters). In order to show feedback to the user that the input is not acceptable, you can use the BeepOnError property or add a Tooltip to show the error message. This feedback mechanism should be implemented in the MaskedInputRejected event handler.

The MaskedTextBox control offers a ValidatingType property to check input that passes the requirements of the Mask, but may not be the correct datatype. The TypeValidationCompleted event is raised after this type validation and you can handle it to determine results.

If you still need to handle keypress events, then read on...!

The method I would recommend in your case is that instead of handling the KeyDown event (you ostensibly do not need advanced key handling capability) or using a Regex to match input (frankly, overkill), I would simply use the built-in properties of the Char structure.

private void maskedTextBox1_KeyPress(object sender, KeyPressEventArgs e)
{
  Char pressedKey = e.KeyChar;
  if (Char.IsLetter(pressedKey) || Char.IsSeparator(pressedKey) || Char.IsPunctuation(pressedKey))
  {
    // Allow input.
    e.Handled = false
  }
  else
    // Stop the character from being entered into the control since not a letter, nor punctuation, nor a space.
    e.Handled = true;
  }
}

Note that this snippet allows you to handle punctutation and separator keys as well.

---

This code will distinguish alphabetic character key presses from non alphabetic ones:

private void maskedTextBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (Regex.IsMatch(e.KeyChar.ToString(), @"p{L}"))
    {
        // this is a letter
    }
    else
    {
        // this is NOT a letter
    }
}

Update: note that the above regex pattern will match ONLY alphabetic characters, so it will not allow spaces, commas, dots and so on. In order to allow more kinds of characters, you will need to add those to the pattern:

// allow alphabetic characters, dots, commas, semicolon, colon 
// and whitespace characters
if (Regex.IsMatch(e.KeyChar.ToString(), @"[p{L}.,;:s]"))

链接地址: http://www.djcxy.com/p/95960.html

上一篇: 创建只接受数字的WPF文本框

下一篇: 如何使文本框只接受字母字符