Update values from modal popup in ASP.Net

Hi MattNorman,

Please refer below code.

Database

I have made use of the following table Customers with the schema as follows.

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

HTML

<div id="simpleModal" class="modal" tabindex="-1" role="dialog">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">
                    Customer Details Form</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body">
                <asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false">
                    <Columns>
                        <asp:BoundField DataField="CustomerId" HeaderText="CustomerId" />
                        <asp:BoundField DataField="Name" HeaderText="Name" />
                        <asp:BoundField DataField="Country" HeaderText="Country" />
                        <asp:TemplateField>
                            <ItemTemplate>
                                <asp:CheckBox ID="cbCountry" runat="server" />
                            </ItemTemplate>
                        </asp:TemplateField>
                    </Columns>
                </asp:GridView>
            </div>
            <div class="modal-footer">
            <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="Submit" />
                <button type="button" class="btn btn-secondary" data-dismiss="modal">
                    Close</button>
            </div>
        </div>
    </div>
</div>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" 
    integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
    crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css"
    integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm"
    crossorigin="anonymous" />
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
    integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
    crossorigin="anonymous"></script>
<script type="text/javascript">
    window.onload = function () {
        OpenBootstrapPopup();
    };
    function OpenBootstrapPopup() {
        $("#simpleModal").modal('show');
    }
</script>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

VB.Net

Imports System.Data
Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

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

protected void Submit(object sender, EventArgs e)
{
    string message = "Checked Ids are:\\n";
    foreach (GridViewRow row in gvCustomers.Rows)
    {
        CheckBox chk = (row.FindControl("cbCountry") as CheckBox);
        if (chk.Checked)
        {
            message += row.Cells[0].Text + "\\n";
        }
    }

    ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('" + message + "');", true);
}

private void BindGrid()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", con))
        {
            con.Open();
            gvCustomers.DataSource = cmd.ExecuteReader();
            gvCustomers.DataBind();
            con.Close();
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.BindGrid()
    End If
End Sub

Protected Sub Submit(ByVal sender As Object, ByVal e As EventArgs)
    Dim message As String = "Checked Ids are:\n"
    For Each row As GridViewRow In gvCustomers.Rows
        Dim chk As CheckBox = (TryCast(row.FindControl("cbCountry"), CheckBox))
        If chk.Checked Then
            message += row.Cells(0).Text & "\n"
        End If
    Next

    ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('" & message & "');", True)
End Sub

Private Sub BindGrid()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Customers", con)
            con.Open()
            gvCustomers.DataSource = cmd.ExecuteReader()
            gvCustomers.DataBind()
            con.Close()
        End Using
    End Using
End Sub

Screenshot