C#Winform读取txt文件

private void btnRead_Click(object sender, EventArgs e)
        {
            string filename = this.txtFilePath.Text.Trim().ToString();
            string print = "";
            if (filename.Length == 0)
            {
                MessageBox.Show("请选择所要读取的文件！");
                return;
            }
            StringBuilder sb = new StringBuilder();

            using (StreamReader sr = new StreamReader(filename, Encoding.Default))
            {
                while ((print = sr.ReadLine()) != null)
                {
                    sb.Append(print + "\r\n");
                }
            }
            this.txtContent.Text = sb.ToString();
            MessageBox.Show("读取成功！");
        }