关于弹出对话框，遇到问题，求助！

问题描述，在一个UpdatePanel里使用GridView控件，其中有一列的ItemTemplate中放入一个TextBox控件和Button控件，我的需求是点击Button按钮，将TextBox中的内容存入数据库，并弹出保存成功对话框。简要代码<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
<asp:GridView ID="GridView1" BorderColor="Black" 
            OnRowDataBound="GridView1_RowDataBound"   runat="server" 
            AutoGenerateColumns="False"  Font-Size="12px" Width="1200px" AllowSorting="True" 
            onrowcancelingedit="GridView1_RowCancelingEdit" 
            OnRowDeleting="GridView1_RowDeleting" OnRowUpdating="GridView1_RowUpdating" 
            OnRowEditing="GridView1_RowEditing" style="margin-bottom: 0px" 
                    onrowcommand="GridView1_RowCommand" >
 <Columns>
//省略其他列
 <asp:TemplateField HeaderText="澄清回复">
                  <ItemTemplate>
  <asp:TextBox ID="txtNBAnswer" runat="server" Width="200px" style='overflow:hidden;height:20px' 
                                        onpropertychange="this.style.height = this.scrollHeight + 'px';" 
                                        oninput="this.style.height = this.scrollHeight + 'px';" 
                                        TextMode="MultiLine" ></asp:TextBox>
                                        
                    <asp:Button ID="BttNBAnswer" runat="server"
                          CausesValidation="false" CommandArgument ="<%# GridView1.Rows.Count %>"  CommandName="SaveNBAnswer" Text="Save"  />
              </ItemTemplate>
               <HeaderStyle  Width="220px" />
              </asp:TemplateField>
          </Columns>
          <HeaderStyle BackColor="#E6F2FF" Font-Size="12px" HorizontalAlign="Center" />
            <RowStyle HorizontalAlign="Center" />
            <PagerStyle HorizontalAlign="Center" />
        </asp:GridView>
    </ContentTemplate>
                </asp:UpdatePanel>
.cs代码 protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "SaveNBAnswer")
        {
            if (txtNBAnswer.Text == "")
            {
                ScriptManager.RegisterStartupScript(this, this.GetType(), "s2", "window.open('澄清回复不能为空，保存失败！');", true);
                GridAllBind();
                return;
            }
            int index = Convert.ToInt32(e.CommandArgument);//get Row index
            DataKey datakey = GridView1.DataKeys[index];
            string ClarityID = datakey["ID"].ToString();
            string NBAnswer = ((TextBox)GridView1.Rows[index].FindControl("txtNBAnswer")).Text;
            string NBAnswerDate = DateTime.Now.ToString();
            string sqlStr = "insert into ClarityAnswer(ClarityID,Answer,AnswerPersonalID,AnswerDate) values('" + ClarityID + "','" + NBAnswer + "','" + PersonalID + "','" + NBAnswerDate + "')";
            if (OperateDB.ExecCmd(sqlStr))
            {
                ScriptManager.RegisterStartupScript(this, this.GetType(), "s1", "window.open('保存成功！');", true);            
            }
            else
            {
                ScriptManager.RegisterStartupScript(this, this.GetType(), "s1", "window.open('保存失败！');", true);            
            }
            GridAllBind();
            return;
        }正常情况应该是弹出对话框，告知保存失败、保存成功或不能为空，可现在确是这样，如下图，请问如何解决？