利用线程把文本文件填充到richTextBox;防止导入大文本文件窗口假死现象

 private void btnDr_Click(object sender, EventArgs e)
        {
            richTextBox1.Text = ""; //richTextBox控件
            labelPercent.Visible = true; //显示当前行数的label
            string path = "";
            OpenFileDialog openFileDialog1 = new OpenFileDialog();
            openFileDialog1.Filter = "文件文件(*.txt)|*.txt";
            if (openFileDialog1.ShowDialog() != DialogResult.OK) return;
            path = openFileDialog1.FileName;
            new Thread((ThreadStart)delegate
            {
                StreamReader sr = new StreamReader(openFileDialog1.FileName, Encoding.GetEncoding("gb2312"));
                int line = 0;
                int lineCount = line + 1;
                string strCount = "";
                string strline = sr.ReadLine();
                while (strline != "" && strline != null && !strline.Equals(""))
                {
                    this.Invoke((EventHandler)delegate { this.labelPercent.Text = "已经读取 " + lineCount.ToString() + " 行"; });
                    this.richTextBox1.Text = this.richTextBox1.Text + strline + "\r\n";
                    strline = sr.ReadLine();
                    line++;
                    lineCount++;
                }

                sr.Close();

            }).Start();
        }