Copy文件

private void bRun_Click(object sender, EventArgs e)
{
    byte[] buffer;
    int blocksize = 4096;
    try
    {
        FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open);
        BinaryReader br = new BinaryReader(fs, new UTF8Encoding());
        MemoryStream ms = new MemoryStream();

        BinaryWriter bw = new BinaryWriter(System.IO.File.Open(saveFileDialog1.FileName, FileMode.Create), new UTF8Encoding());        

        buffer = new byte[blocksize];
        int bytesreaded;//always = blocksize
        while ((bytesreaded = br.Read(buffer, 0, blocksize))>0)
        {
            ms.Write(buffer, 0, bytesreaded);
            bw.Write(buffer);  
        }

        bw.Close();
        ms.Close();
        fs.Close();
        MessageBox.Show("Done!");
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    } 
}