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！");
}