C#keypress事件进不去，为什么？

功能需求是回车键和tab键的功能要求一样，但是回车键按下后，keypress事件可以进去，但是tab键按下，keypress事件进不去，为什么？

        private void TextBoxKeypressBit14(object sender, KeyPressEventArgs e)
        {
            if ((e.KeyChar == 13) || (e.KeyChar == (char)Keys.Tab))
            {
                e.Handled = true;
                TextBox tb = (TextBox)sender;
                string tbname = tb.Name;
                string txt = tb.Text;
                int x = Convert.ToInt32(tbname.Substring(7, 3));
                string xuhao = "";
                for (int i = 0; i < alldevices.Count / 10; i++)
                {
                    if (alldevices[i * 10] == label49.Text)
                    {
                        xuhao = alldevices[i * 10 + 8];
                    }
                }

                //if (txt == "") { txt=;}
                try
                {
                    string strMsg = "update Bit14 " + xuhao + " 数据" + (x - 140).ToString() + " " + txt;
                    byte[] buffer = new byte[2048];
                    buffer = Encoding.Default.GetBytes(strMsg);
                    int receive = Program.socketSend.Send(buffer);
                }
                catch { }
                Receive();
                if (x == 180)
                {
                    textBox141.Focus();
                }
                else { this.groupBox5.Controls["textBox" + (x + 1).ToString()].Focus(); }

                for (int i = 0; i < 40; i++)
                {
                    yuan[i] = this.groupBox5.Controls["textBox" + (i + 141).ToString()].Text;
                }
            }
            if(e.KeyChar==27)
            {
                for (int i = 0; i < 40; i++)
                {
                    this.groupBox5.Controls["textBox" + (i + 141).ToString()].Text = yuan[i];
                }
            }
        }

tab键本身自带就是换标签元素的功能吧

一些按键,比如TAB,RETURN,ESC和箭头键不被认为是输入按键被忽略.
通过处理PreviewKeyDown控件事件可以将这些键设置为输入键.
private void textBox1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
{
if(e.KeyData == Keys.Tab)
{
MessageBox.Show("Tab");
e.IsInputKey = true;
}
if (e.KeyData == (Keys.Tab | Keys.Shift))
{
MessageBox.Show("Shift + Tab");
e.IsInputKey = true;
}
}