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！");        }