C# 为什么在onchangetext事件中键入时它什么都不做？

当事件TextChanged中的代码在事件TextBoxURL_KeyDown中时，它也可以很好地使用我想要的逻辑。但是后来我不得不按enter键，所以我把它移到了TextChanged事件中，但是现在当我在TextBoxUrl中键入一个有效的时，什么也没有发生

代码：

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TextChanged在文本框的出口处激发。您可能正在寻找KeyDown或KeyUp，或KeyPress-可能是KeyUp，因为这将允许您在添加新字符后捕获文本框中的内容。

该定义看起来有误……您没有实现事件处理程序，而是在掩盖一个事件处理程序。去掉新的关键字。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace DownloadMultipleFiles
{
    public partial class AddNewDownloads : Form
    {
        public AddNewDownloads()
        {
            InitializeComponent();

            foreach (Control ctrl in this.Controls)
            {
                if ((ctrl as TextBox) != null)
                {
                    (ctrl as TextBox).TextChanged += TextChanged;
                }
            }

            this.TextBoxURL.KeyDown += new KeyEventHandler(TextBoxURL_KeyDown); //add keyDown event
            if (TextBoxFilename.Text == "" || TextBoxBrowse.Text == "")
            {
                TextBoxFilename.Enabled = false;
                TextBoxBrowse.Enabled = false;
                btnOK.Enabled = false;
            }
        }

        private void AddNewDownloads_Load(object sender, EventArgs e)
        {

        }

        private void btnBrowse_Click(object sender, EventArgs e)
        {

        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnOK_Click(object sender, EventArgs e)
        {

        }

        private void TextBoxURL_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter) //validate the URL when you press the Enter key
            {

            }
        }
        private bool CheckValidUrl() // validate from clipboard
        {
            string isUrl = Clipboard.GetText();
            Uri uriResult;
            bool result = Uri.TryCreate(isUrl, UriKind.Absolute, out uriResult)
                && (uriResult.Scheme == Uri.UriSchemeHttp || uriResult.Scheme == Uri.UriSchemeHttps);
            return result;
        }
        private bool WriteValidUrl() // validate manual input 
        {
            string pattern2 = @"^http://www.[a-z].com$";
            Match match = Regex.Match(TextBoxURL.Text, pattern2);
            if (match.Success)
                return true;
            else
                return false;
        }

        private new void TextChanged(object sender, EventArgs e)
        {
            if (CheckValidUrl() == true || WriteValidUrl() == true)
            {
                TextBoxFilename.Enabled = true;
                TextBoxBrowse.Enabled = true;
                btnOK.Enabled = true;
            }
            else
            {
                TextBoxFilename.Enabled = false;
                TextBoxBrowse.Enabled = false;
                btnOK.Enabled = false;
            }
            if (TextBoxURL.Text == "")
            {
                TextBoxFilename.Enabled = false;
                TextBoxBrowse.Enabled = false;
                btnOK.Enabled = false;
            }
        }
    }
}