如何返回键值?也就是说,如果我想在文本框中只允许整数值,怎样可以防止用户输入非整数值呢?关于 KeyPress
事件,我知道还有其他方法可以匹配字符串值,但我想要的是不允许在文本框中输入无效的值。
if (( value >0 a&&(value <=9)) then
assigned
else
return
e.Handled = true;
MSDN上的示例:链接
// 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;
}
}
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!Char.IsDigit(e.KeyChar)) e.Handled = true;
}
创建一个包含允许用户输入的字符的字符串。
使用 KeyDown
或 KeyUp
处理特殊键。
private void tbN1_KeyPress(object sender, KeyPressEventArgs e)
{
String sKeys = "1234567890ABCDEF";
if (!sKeys.Contains(e.KeyChar.ToString().ToUpper()))
e.Handled = true;
}
从技术上讲,这是错误的,因为您标记了您的问题WPF。但是,既然您接受了其他Windows Forms答案,我将发布我的解决方案,该解决方案适用于实数而非整数。它还本地化为仅接受当前语言环境的小数分隔符。
private void doubleTextBox_KeyPress (object sender, KeyPressEventArgs e)
{
var textBox = sender as TextBoxBase;
if (textBox == null)
return;
// did the user press their locale's decimal separator?
if (e.KeyChar.ToString() == CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator)
{
if (textBox.Text.Length == 0) // if empty, prefix the decimal with a 0
{
textBox.Text = "0" + CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
e.Handled = true;
textBox.SelectionStart = textBox.TextLength;
}
// ignore extra decimal separators
else if (textBox.Text.Contains(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator))
e.Handled = true;
}
// allow backspaces, but no other non-numeric characters;
// note that arrow keys, delete, home, end, etc. do not trigger KeyPress
else if (e.KeyChar != '\b' && (e.KeyChar < '0' || e.KeyChar > '9'))
e.Handled = true;
}
对于WPF,使用类似以下代码的PreviewTextInput事件:
// Filter out non-numeric keys.
private void MyApp_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
String sKeys = "1234567890";
if (!sKeys.Contains(e.Text))
e.Handled = true;
}
Protected Overrides Sub OnTextInput(ByVal e As System.Windows.Input.TextCompositionEventArgs)
Dim newChar As Char = Convert.ToChar(e.Text)
If Not [Char].IsDigit(newChar) Then e.Handled = True
End Sub
C# 版本
protected override void OnTextInput(System.Windows.Input.TextCompositionEventArgs e)
{
char newChar = Convert.ToChar(e.Text);
if (!Char.IsDigit(newChar)) e.Handled = true;
}
MaskedTextBox
并强制其仅接受整数。