文件上传到数据库，文件看起来像乱码

Question

我有这个代码，当我上传文件并查看gridview时，它看起来像下面的图片，我不知道为什么。此外，ContentType列也显示为空，我怀疑这与搞砸的上传有关。评论和GUID有效。没有出现错误消息。

protected void ButtonSubmit_Click(object sender, EventArgs e)
{
    try
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);

        string filePath = FileUpload1.PostedFile.FileName;
        string filename = Path.GetFileName(filePath);
        string ext = Path.GetExtension(filename);
        string contenttype = String.Empty;

        switch (ext)
        {
            case ".doc":
                contenttype = "application/vnd.ms-word";
                break;
            case ".docx":
                contenttype = "application/vnd.ms-word";
                break;
            case ".xls":
                contenttype = "application/vnd.ms-excel";
                break;
            case ".xlsx":
                contenttype = "application/vnd.ms-excel";
                break;
            case ".jpg":
                contenttype = "image/jpg";
                break;
            case ".png":
                contenttype = "image/png";
                break;
            case ".gif":
                contenttype = "image/gif";
                break;
            case ".pdf":
                contenttype = "application/pdf";
                break;
        }

        Stream fs = FileUpload1.PostedFile.InputStream;
        BinaryReader br = new BinaryReader(fs);
        Byte[] bytes = br.ReadBytes((Int32)fs.Length);

        Guid newGUID = Guid.NewGuid();

        conn.Open();

        string InsertUser = "INSERT INTO UserUpload (ID, Comment,DataUpload, ContentType) VALUES (@ID, @Comment, @DataUpload, @ContentType)";

        SqlCommand com = new SqlCommand(InsertUser, conn);

        com.Parameters.AddWithValue("@ID", newGUID.ToString());
        com.Parameters.AddWithValue("@Comment", TextBoxComment.Text);
        com.Parameters.AddWithValue("@DataUpload", SqlDbType.VarChar).Value = bytes;
        com.Parameters.Add("@ContentType", SqlDbType.VarChar).Value = contenttype;

        com.ExecuteNonQuery();
        LabelMessage.Text = ("Your Upload Is Complete");         

        conn.Close();

    }
    catch (Exception ex)
    {

        LabelMessage.Text = ("Error:" + ex.Message);

    }
}