关于上传图片怎么自动缩放成框架的比例！

Question

try
            {
                OpenFileDialog openFileDialog1 = new OpenFileDialog();
                openFileDialog1.Filter = "picture files (*.jpg)|*.jpg|All files (*.*)|*.*";
                if (openFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    //避免选择了正在使用的图片
                    if (pictureBox1.Image != null)
                    {
                        pictureBox1.Image.Dispose();
                        pictureBox1.Image = null;
                    }
                    //保存到临时文件夹
                    FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open);
                    byte[] buffer = new byte[(int)fs.Length];
                    fs.Read(buffer, 0, buffer.Length);
                    fs.Close();
                    FileStream fs1 = new FileStream(@"d:\客户资料管理系统\3", FileMode.Create);
                    fs1.Write(buffer, 0, buffer.Length);
                    fs1.Close();
                    //显示图片
                    pictureBox1.Image = Image.FromFile(openFileDialog1.FileName);
                }
            }catch{ MessageBox.Show("你选择的照片正在被使用，请另选！", "添加失败", MessageBoxButtons.OK, MessageBoxIcon.Warning);}
我用这个方法上传的图片怎么缩放成框架的比例啊 
  求那位大侠帮帮忙 
 谢谢了