Rotate Image in Clockwise in c#

string filename;

public Form1()

{

InitializeComponent();

filename = null;

}

private void button3_Click(object sender, EventArgs e)

{

// OPEN

OpenFileDialog open = new OpenFileDialog();

if (open.ShowDialog() == DialogResult.OK)

{

filename = open.FileName;

pictureBox1.Image = Image.FromFile(filename);

}

private void button1_Click(object sender, EventArgs e)

{

// CLOCKWISE

Image i = pictureBox1.Image;

i.RotateFlip(RotateFlipType.Rotate90FlipXY);

pictureBox1.Image = i;

i.Save(filename);

}