find a mistake from code actually this coding not upload fi

Question

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;


namespace UploadNewItem1.Utilities
{
    public class FileUtilities
    {
        private static string GetConnectionString()
        {
            return ConfigurationManager.AppSettings["DBConnectionString"];
        }

        private static void OpenConnection(SqlConnection connection)
        {
            connection.ConnectionString = GetConnectionString();
            connection.Open();
        }

        // Get the list of the files in the database
        public static DataTable GetFileList()
        {
            DataTable fileList = new DataTable();
            using (SqlConnection connection = new SqlConnection())
            {
                OpenConnection(connection);
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = connection;
                cmd.CommandTimeout = 0;

                cmd.CommandText = "SELECT ID, Name, ContentType, Size FROM Files";
                cmd.CommandType = CommandType.Text;
                SqlDataAdapter adapter = new SqlDataAdapter();

                adapter.SelectCommand = cmd;
                adapter.Fill(fileList);

                connection.Close();
            }

            return fileList;
        }

        // Save a file into the database
        public static void SaveFile(string name, string contentType,
            int size, byte[] data)
        {
            using (SqlConnection connection = new SqlConnection())
            {
                OpenConnection(connection);
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = connection;
                cmd.CommandTimeout = 0;

                string commandText = "INSERT INTO Files VALUES(@Name, @ContentType, ";
                commandText = commandText + "@Size, @Data)";
                cmd.CommandText = commandText;
                cmd.CommandType = CommandType.Text;

                cmd.Parameters.Add("@Name", SqlDbType.NVarChar, 100);
                cmd.Parameters.Add("@ContentType", SqlDbType.VarChar, 50);
                cmd.Parameters.Add("@size", SqlDbType.Int);
                cmd.Parameters.Add("@Data", SqlDbType.VarBinary);

                cmd.Parameters["@Name"].Value = name;
                cmd.Parameters["@ContentType"].Value = contentType;
                cmd.Parameters["@size"].Value = size;
                cmd.Parameters["@Data"].Value = data;
                cmd.ExecuteNonQuery();

                connection.Close();
            }
        }

        // Get a file from the database by ID
        public static DataTable GetAFile(int id)
        {
            DataTable file = new DataTable();
            using (SqlConnection connection = new SqlConnection())
            {
                OpenConnection(connection);
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = connection;
                cmd.CommandTimeout = 0;

                cmd.CommandText = "SELECT ID, Name, ContentType, Size, Data FROM Files "
                    + "WHERE ID=@ID";
                cmd.CommandType = CommandType.Text;
                SqlDataAdapter adapter = new SqlDataAdapter();

                cmd.Parameters.Add("@ID", SqlDbType.Int);
                cmd.Parameters["@ID"].Value = id;

                adapter.SelectCommand = cmd;
                adapter.Fill(file);

                connection.Close();
            }

            return file;
        }



    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (! IsPostBack)
            {
                DataTable fileList = FileUtilities.GetFileList();
                gvFiles.DataSource = fileList;
                gvFiles.DataBind();
            }
        }
 
        protected void btnUpload_Click(object sender, EventArgs e)
        {
            // Although I put only one http file control on the aspx page,
            // the following code can handle multiple file controls in a single aspx page.
            HttpFileCollection files = Request.Files;
            foreach (string fileTagName in files)
            {
                HttpPostedFile file = Request.Files[fileTagName];
                if (file.ContentLength > 0)
                {
                    // Due to the limit of the max for a int type, the largest file can be
                    // uploaded is 2147483647, which is very large anyway.
                    int size = file.ContentLength;
                    string name = file.FileName;
                    int position = name.LastIndexOf("\\");
                    name = name.Substring(position + 1);
                    string contentType = file.ContentType;
                    byte[] fileData = new byte[size];
                    file.InputStream.Read(fileData, 0, size);
 
                    FileUtilities.SaveFile(name, contentType, size, fileData);
                }                
            }
 
            DataTable fileList = FileUtilities.GetFileList();
            gvFiles.DataSource = fileList;
            gvFiles.DataBind();
        }
    }
        
    public partial class GetFile : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            // Get the file id from the query string
            int id = Convert.ToInt16(Request.QueryString["ID"]);
 
            // Get the file from the database
            DataTable file = FileUtilities.GetAFile(id);
            DataRow row = file.Rows[0];
 
            string name = (string)row["Name"];
            string contentType = (string)row["ContentType"];
            Byte[] data = (Byte[])row["Data"];
 
            // Send the file to the browser
            Response.AddHeader("Content-type", contentType);
            Response.AddHeader("Content-Disposition", "attachment; filename=" + name);
            Response.BinaryWrite(data);
            Response.Flush();
            Response.End();
        }
    }
}
}   
[find the error  from code actually  this coding not upload file in database ] urgent