This code for image rotation is simple so we will start step by step.

Step 1) Take an image and button control; code like:

{
<form id="form1" runat="server">
 <div>
<asp:Image ID="Image1" runat="server" Height="178px" Width="247px
ImageUrl="~/images/2168NN97_4[1].jpg" />
</div>
 <asp:Button ID="Button1" runat="server" Text=">>"
OnClick="Button1_Click"/>
}

Step 2) Double-click on the button and write code as follows:

{
protected void Button1_Click(object sender, EventArgs e)
 {
 string p = Server.MapPath(Image1.ImageUrl);
 System.Drawing.Image i = System.Drawing.Image.FromFile(p);
 i.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipX);
 i.Save(p);
 i.Dispose();
 Image1.Attributes.Add("ImageUrl",p);
}
}

Step 3)

Now execute the application and verify that it runs as expected.