文件下载格式不正确

好的，

基本上我已经能够使用asp.net和c#上传文件到SQL server数据库。我可以在浏览器中查看它们没有问题，但是当我下载它们时，它们似乎失去了原始格式，例如word文档失去了docx扩展名，您必须手动选择将它们打开为word文档。

这是我到目前为止的代码

    //Method used to upload a file to the database
    protected void UploadBut_Click(object sender, EventArgs e)
    {
        Stream inpStream = DocumentsUploadControl.PostedFile.InputStream;
        BinaryReader br = new BinaryReader(inpStream);
        Byte[] size = br.ReadBytes ((int)inpStream.Length);
        using (SqlConnection conn = new SqlConnection("Data Source=conn''sqlexpress;Initial Catalog=new catalog;Integrated Security=True"))
        {
            string sql = "INSERT INTO Attachments(AttachmentReferenceID, AttachmentType, Filename, AttachmentDescription, FileUploadedBy, UploadDate)" + 
                "values (@Reference, @Type, @Filename, @Descr, @UploadedBy, @UploadedDate)";
            using (SqlCommand cmd = new SqlCommand(sql, conn))
            {
                cmd.Parameters.AddWithValue("@Reference", ReferenceDDL.Text.Trim());
                cmd.Parameters.AddWithValue("@Type", DocumentsUploadControl.PostedFile.ContentType.ToString());
                cmd.Parameters.AddWithValue("@Filename", FilenameTB.Text.Trim());
                cmd.Parameters.AddWithValue("@Descr", size);
                cmd.Parameters.AddWithValue("@UploadedBy", Session["username"].ToString());
                cmd.Parameters.AddWithValue("@UploadedDate", DateTime.Now.Date.ToShortDateString());
                conn.Open();
                cmd.ExecuteNonQuery();
                conn.Close();
                Response.Redirect("Documents.aspx");
            }
        }
    }

    //listener used to download the file
    protected void lnkDownload_Click(object sender, EventArgs e)
    {
        LinkButton lnkbtn = sender as LinkButton;
        GridViewRow gvrow = lnkbtn.NamingContainer as GridViewRow;
        int fileId = Convert.ToInt32(DocumentsGridView.DataKeys[gvrow.RowIndex].Value.ToString());
        using (SqlConnection conn = new SqlConnection("Data Source=conn''sqlexpress;Initial Catalog=new catalog;Integrated Security=True"))
        {
            string sql = "SELECT AttachmentReferenceID, AttachmentType, Filename, AttachmentDescription, FileUploadedBy, UploadDate FROM Attachments WHERE AttachmentID=@ID";
            using (SqlCommand cmd = new SqlCommand(sql, conn))
            {
                cmd.Parameters.AddWithValue("@ID", fileId);
                conn.Open();
                SqlDataReader dr = cmd.ExecuteReader();
                if (dr.Read())
                {
                    Response.ContentType = dr["AttachmentType"].ToString();
                    Response.AddHeader("Content-Disposition", "attachment;filename='"" + dr["Filename"] + "'"");
                    Response.BinaryWrite((byte[])dr["AttachmentDescription"]);
                    Response.End();
                    conn.Close();
                }
            }
        }
    }

Response.contenttype = "application/" + dr["attachmenttype"].ToString();

Response.AddHeader("Content-Disposition", "attachment;filename='"" + dr["Filename"] + "." + dr["AttachmentType"].ToString());