Question

如何禁止在textBox中引入字母？也就是说，这种结构不正确

public void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    try
    {
        char s = Convert.ToChar(textBox1.Text);
        if ((s <= '0') || (s >= '9'))
            MessageBox.Show("You have entered a symbol! Please enter a number");
    }
    catch (System.FormatException)
    {
        MessageBox.Show("You have entered a symbol! Please enter a number");
    }
}

Answer 1

您需要检查在KeyDown事件（e.Key属性）中输入的密钥，因为在事件发生后将键值添加到Text字段或使用TextChanged事件 - 这将捕获cut＆amp;粘贴操作。

public void textBox1_TextChanged(object sender, TextChangedEventArgs e)
{        
    if (!ValidNumericString(textBox1.Text))
    {
        MessageBox.Show("You have entered invalid characters! Please enter a number");
        Dispatcher.BeginInvoke(new Action(() => textBox1.Undo()));
        e.Handled = true;
    }
}

public bool ValidNumericString(string IPString)
{
    return IPString.All(char.IsDigit);
    // OR make this check for thousands & decimals if required
}

Answer 2

您可以使用OnKeyPress事件，如果您愿意，可以手动取消键事件。

void textBox1_OnKeyPress(KeyPressEventArgs e)
{
    e.Handled = true;   // this won't send the key event to the textbox
}

如果您只想接受数字和相关字符（负号，小数分隔符......），您可以测试输入的字符：

void textBox1_OnKeyPress(KeyPressEventArgs e)
{
    NumberFormatInfo numberFormatInfo = CultureInfo.CurrentCulture.NumberFormat;
    string decimalSeparator = numberFormatInfo.NumberDecimalSeparator;
    string groupSeparator = numberFormatInfo.NumberGroupSeparator;
    string negativeSign = numberFormatInfo.NegativeSign;

    string keyInput = e.KeyChar.ToString();

    e.Handled = !(Char.IsDigit(e.KeyChar) || keyInput.Equals(negativeSign) || keyInput.Equals(decimalSeparator) || keyInput.Equals(groupSeparator));
}

这是未经测试的代码，因为我在工作，但你明白了。

Answer 3

    private void textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        if (Control.ModifierKeys == Keys.Control) return; // Check if ctrl is pressed
        var key = (char) e.KeyValue; // ASCII to char
        if (char.IsDigit(key) || char.IsControl(key) || char.IsWhiteSpace(key)) return; // Check if "key" is a number
        MessageBox.Show("You have entered a symbol! Please enter a number"); 
        textBox1.Text = textBox1.Text.Substring(0, textBox1.Text.Length - 1); // Remove last element
        textBox1.SelectionStart = textBox1.Text.Length; // Return to initial position
    }

禁止输入字母textBox

3 个答案: