在C＃中按下键时，UserControl没有引发KeyPress事件

Question

我想创建一个文本框，允许用户仅输入正双精度数。为此，我创建了一个从System.Windows.Forms.Textbox继承的类，并添加了一个KeyPress事件，如下所示：

    public partial class PositiveDoubleOnlyTB : TextBox
    {
        private void InitializeComponent()
        {            
            this.SuspendLayout();
            // 
            // PositiveDoubleOnlyTB
            // 
            this.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.PositiveDoubleOnlyTB_KeyPress);
            this.ResumeLayout(false);

        }

        private void PositiveDoubleOnlyTB_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
                (e.KeyChar != '.'))
            {
                e.Handled = true;
                SystemSounds.Beep.Play();
            }

            // only allow one decimal point
            if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
            {
                e.Handled = true;
                SystemSounds.Beep.Play();
            }

        }
    }

问题是，当我在此自定义TextBox中输入数据时，不会引发KeyPress事件。有人可以帮我显示出什么问题吗？

Answer 1

public class PositiveDoubleOnlyTB : TextBox
{
    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        if (!(char.IsDigit(e.KeyChar) || e.KeyChar == '.' && base.Text.IndexOf('.') == -1))
        {
            e.Handled = true;
        }

        base.OnKeyPress(e);
    }
}