Winform窗体使用FileStream读写文件

private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
{
OpenFileDialog ofd = new OpenFileDialog();
ofd.Title = "请打开一个文件";
ofd.InitialDirectory = @"C:\Users\Administrator\Desktop";
ofd.Multiselect = true;
ofd.Filter = "文本文件|*.txt|word文档|*.doc|pdf文档|*.pdf";
ofd.ShowDialog();

string path = ofd.FileName;
list.Add(path);

string fileName = Path.GetFileName(path);
listBox1.Items.Add(fileName);

if (path == "")
{
return;
}
using (FileStream fsRead = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Read))
{
byte[] buffer = new byte[1024 * 1024 * 5];
int r = fsRead.Read(buffer, 0, buffer.Length);
textBox1.Text = Encoding.Default.GetString(buffer, 0, r);
}
}

private void 保存ToolStripMenuItem_Click(object sender, EventArgs e)
{
SaveFileDialog sfd = new SaveFileDialog();
sfd.Title = "请选择保存的位置";
sfd.InitialDirectory = @"C:\Users\Administrator\Desktop";
sfd.Filter = "文本文件|*.txt|word文档|*.doc|pdf文档|*.pdf";
sfd.ShowDialog();

string path = sfd.FileName;
if (path == "")
{
return;
}
using(FileStream fsWrite=new FileStream(path,FileMode.OpenOrCreate,FileAccess.Write))
{
byte[] buffer=Encoding.Default.GetBytes(textBox1.Text);
fsWrite.Write(buffer, 0, buffer.Length);
}
MessageBox.Show("保存成功");
}