<asp:TextBox runat="server"
        ID="txtComment"
        TextMode="MultiLine"
        Columns="50"
        Rows="10"
        Text="А что думаете вы ?" />

    <asp:TextBox Visible="false" ID="txtClipLineID" Text="0" runat="server"></asp:TextBox>
    <asp:TextBox Visible="false" ID="txtAccount_UserID" Text="1" runat="server"></asp:TextBox>
    <asp:Button ID="btnAddComment" runat="server" Text="Добавить" OnClick="btnAddComment_Click" />

  protected void btnAddComment_Click(object sender, EventArgs e)
        {
            ClipLine com = new ClipLine();
            com.DateComment = DateTime.Now;
            com.Comment = Server.HtmlEncode(txtComment.Text);
            com.Account_UserID = Convert.ToInt32(txtAccount_UserID.Text);
            com.Clip_ClipID = ClipID;
            com.ClipLineID = Convert.ToInt32(txtClipLineID.Text);
            repo.SaveComment(com);
            txtComment.Text = "";
        }