取消按鍵事件

Question

如何返回密鑰？意思是如果我想只允許整數值在文本框中，我怎麼能不允許用戶輸入非整數，關於KeyPress事件，我知道還有其他一些方法，如表達式匹配字符串值，但我不想將無效值賦給文本框。

if ((value >0 a&&(value <=9)) then 
    assigned 
else 
    return 

Answer 1

從MSDN使用Handled屬性

e.Handled = true; 

例子：link

// 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; 
    } 
} 

Answer 2

你可以使用MaskedTextBox，並迫使它整數只。

Answer 3

您可以從文本框，然後繼承：

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; 
} 

Answer 4

您，可以按以下使用按鍵事件。使用e.Handled爲true來取消用戶輸入

private void textBox1_KeyPress(object sender, KeyPressEventArgs e) 
    { 
     if (!Char.IsDigit(e.KeyChar)) e.Handled = true; 
    } 

Answer 5

使用您允許用戶輸入的字符創建一個字符串。

使用KeyDown或KeyUp處理特殊鍵

private void tbN1_KeyPress(object sender, KeyPressEventArgs e) 
{ 
    String sKeys = "1234567890ABCDEF"; 
    if (!sKeys.Contains(e.KeyChar.ToString().ToUpper())) 
     e.Handled = true; 
} 

Answer 6

從技術上講，這是因爲你標記你的問題WPF錯誤。但是，既然你接受了其他Windows窗體的答案，我會發布我的解決方案，它適用於實數而不是整數。它也被本地化爲僅接受當前區域的小數點分隔符。

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; 
}