winform in listening TextBox, send a carriage return, shift carriage return line

Monitor KeyUpevents Btn_Senderas the Send button

/// <summary>
/// 监听换行
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void TextBox_KeyUp(object sender, KeyEventArgs e)
{
    //Shift+Enter换行
    if (e.Modifiers == Keys.Shift && e.KeyCode == Keys.Enter){}
    //发送
    else if (e.KeyCode == Keys.Enter)
    {
        //取消回车符
        var str = txt_Sender.Text;
        if (str.EndsWith(Environment.NewLine)) 
        {
            txt_Sender.Text = str.Substring(0, str.Length - Environment.NewLine.Length);
            Btn_Sender_Click(null, null);
        }
    }
}

Above if()...else if()...facilitate understanding, equivalent to the following

//Shift+Enter换行
//发送
if (!((e.Modifiers == Keys.Shift && e.KeyCode == Keys.Enter) || e.KeyCode != Keys.Enter))
{
    //取消回车符
    var str = txt_Sender.Text;
    if (str.EndsWith(Environment.NewLine)) 
    {
        txt_Sender.Text = str.Substring(0, str.Length - Environment.NewLine.Length);
        Btn_Sender_Click(null, null);
    }
}