将图片从picturebox插入数据库

Question

namespace dota2
{
  public partial class Form1 : Form
  {
    private SqlConnection cn = new SqlConnection();
    private SqlCommand cmd = new SqlCommand();
    private SqlDataReader dr;
    private SqlParameter picture;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        SqlConnection cn = new SqlConnection(global::dota2.Properties.Settings.Default.Database1ConnectionString);
        cmd.Connection = cn;
        picture = new SqlParameter("@picture", SqlDbType.Image);

    }

    private void button1_Click(object sender, EventArgs e)
    {
        open();
    }

    private void button2_Click(object sender, EventArgs e)
    {
        savepicture();

    }
    private void savepicture()
    {

        if (pictureBox1.Image != null)
        {
            MemoryStream ms = new MemoryStream();
            pictureBox1.Image.Save(ms, pictureBox1.Image.RawFormat);
            byte[] a = ms.GetBuffer();
            ms.Close();
            cmd.Parameters.Clear();
            cmd.Parameters.AddWithValue("@picture", a);
            cmd.CommandText = "insert into pictures (name,picture) values ('" + textBox1.Text.ToString() + "',@picture)";
            cn.Open();
            cmd.ExecuteNonQuery();
            cn.Close();
            textBox1.Text = "";
            pictureBox1.Image = null;
            MessageBox.Show("Image Saved", "Programming At Kstark");
        }
    }
    private void open()
    {
        try
        {
            OpenFileDialog f = new OpenFileDialog();
            f.InitialDirectory = "C:/Picture/";
            f.Filter = "All Files|*.*|JPEGs|*.jpg|Bitmaps|*.bmp|GIFs|*.gif";
            f.FilterIndex = 0;
            if (f.ShowDialog() == DialogResult.OK)
            {
                pictureBox1.Image = Image.FromFile(f.FileName);
                pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
                pictureBox1.BorderStyle = BorderStyle.Fixed3D;
                textBox1.Text = f.SafeFileName.ToString();
            }
        }
        catch { }
    }
  }
}

我的表单有一个图片框以及Open和Save按钮。我试图使用下面的代码将图片从我的图片框插入数据库。图片按原样打开并显示在图片框中，但按下保存按钮不起作用。它说要么cn。打开是一个错误或执行查询。