c# - 允许文本框仅支持数字和 OemMinus？

Question

在我的代码中，我使用这段代码来验证仅支持的文本框，但我想允许 OemMinus (-) 我该怎么做？

private void card_No_KeyDown(object sender, KeyEventArgs e)
{
    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 && 
                                        e.KeyCode == Keys.Oemplus)
        {
            // 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;
            }
        }
    }
}

private void card_No_KeyPress(object sender, KeyPressEventArgs e)
{
    if (nonNumberEntered == true)
    {
        MessageBox.Show("not allowed");
        e.Handled = true;
    }
}

Answer 1

你可以像这样处理 KeyPress 事件

private void card_No_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!char.IsNumber(e.KeyChar) && e.KeyChar != '-' && e.KeyChar != (char)Keys.Back)
       e.Handled = true;
}

但这不会阻止用户复制粘贴无效值，因此您还可以处理 TextChanged 事件。

private void card_No_TextChanged(object sender, EventArgs e)
{
    if (!String.IsNullOrEmpty(card_No.Text))
    {
        if (Regex.Matches(card_No.Text, @"(-|\d)").Count != card_No.Text.Length)
        {
            //pasted an invalid value
            MessageBox.Show("Invalid value entered");
        }
    }
}