如何在asp.net循环期间显示确认警报消息框

Question

During a loop of adding to new datarow in datatable, I want to show a confirmation box on specific condition. So if user select "yes", the row will add to table or skip and loop will continue. For this I used ModalPopupExtender but problem is that modal is popup only after loop is completed, which useless in my case.

Here my code: Loop:

for(int i=0;i<dt2.Rows.count;i++)
{
 ....
 ....
 ....


        if (l > 0)
        {
             DataRow row = datarow1(dt2,dt3,i);                        
             dt3.Rows.Add(row);
        }
        else
        {
             ModalPopupExtender1.Show();
                if ((bool)ViewState["cnfirm"] == true)
                {
                     DataRow row = datarow1(dt2, dt3, i);
                     dt3.Rows.Add(row);
                }
                
        }
}

And

protected void Decision_Command(object sender, CommandEventArgs e)
    {
        if (e.CommandArgument == "Yes")
        {
            ViewState["cnfirm"] = true;
        }
        else
        {
            ViewState["cnfirm"] = false;
        }

    }

Please help to resolve this issue or suggest another/easiest way.

Answer 1

As noted, you need to let the page render - you can't interact with user DURING a page create process - only after, and only after the page travels down to user.

You are much better off to do this:

Say our gride - drop in a check box.

So, markup is this:

<div style="width:50%;padding:25px; margin-left: 40px;">

<asp:GridView ID="GVHotels" runat="server" AutoGenerateColumns="False" 
    DataKeyNames="ID" CssClass="table"  >
    <Columns>
        <asp:BoundField DataField="FirstName"   HeaderText="FirstName" />
        <asp:BoundField DataField="LastName"    HeaderText="LastName"  />
        <asp:BoundField DataField="City"        HeaderText="City" />
        <asp:BoundField DataField="HotelName"   HeaderText="HotelName"  />
        <asp:BoundField DataField="Description" HeaderText="Description"  />

        <asp:TemplateField HeaderText="To Process" ItemStyle-HorizontalAlign="Center">
            <ItemTemplate>
                <asp:CheckBox ID="chkSel" runat="server" CssClass="bigcheck" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

    <asp:Button ID="cmdProcess" runat="server" Text="Process selected" CssClass="btn" Width="153px"  />
    <br />
    <br />

And code to fill is this:

   protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
            LoadGrid();
    }

    void LoadGrid()
    {
        using (SqlConnection conn = new SqlConnection(Properties.Settings.Default.TEST4))
        {
            using (SqlCommand cmdSQL = new SqlCommand("SELECT * from tblHotels ORDER by HotelName", conn))
            {
                conn.Open();
                DataTable rstData = new DataTable();
                rstData.Load(cmdSQL.ExecuteReader());
                GVHotels.DataSource = rstData;
                GVHotels.DataBind();
            }
        }
    }

Output is now this:

And now it is a simple process to check for the check box like this:

   protected void cmdProcess_Click(object sender, EventArgs e)
    {
        foreach (GridViewRow gRow in GVHotels.Rows)
        {
            CheckBox ckSel = (CheckBox)gRow.FindControl("chkSel");

            if (ckSel.Checked)
            {
                int PKID = (int)GVHotels.DataKeys[gRow.RowIndex]["ID"];

                // code here to process data based on database PKID
                Debug.Print("to process database PK ID = " + PKID);                    
            }
        }
    }

So, you can't interact with the user DURING the loop - that loop is running server side, and the browser is waiting for the WHOLE page to come back. Only AFTER all code behind runs does the whole copy of the web page travel back to the client.

You can certainly replace the check box with a button, and pop a cool dialog box to ask for yes/no, or delete this for each row - but there not a practical way to do this in that loop. So, code behind MUST finish, MUST exit, and then and only then does the WHOLE page get send down to client side. Once that has occurred, then you can start to interact with the user. As noted, in place of a check box, you could drop in a button - delete this, or remove this? And that can be nice looking dialog box (say bootstrap, or better jQuery.UI dialog). So you can conditional prompt the user - but only after the page has rendered client side.