Modal Popup

Question

Hi

I have below code & i want when clicked on Add modal popup opens & in Dropdown i want to display States of selected record in a dropdown

try
{
    StringBuilder htmlTable = new StringBuilder();
    string ParticipantType = "";

    BALTrainingHeader bALTrainingHeader = new BALTrainingHeader();
    List<TrainingHeader> Result = bALTrainingHeader.GetRecordListDrafted();

    if (Result != null)
    {
        BALEmployee bALEmployee = new BALEmployee();
        htmlTable.Append("<table class='table table-bordered table-hover datatable-highlight' id='tbldata'>");
        htmlTable.Append("<thead><tr><th style='display:none'>#</th><th>Training Number</th><th class='text-center nosort'>Add</th></tr></thead>");
        htmlTable.Append("<tbody>");
        foreach (var colum in Result)
        {
            htmlTable.Append("<tr>");
            htmlTable.Append("<td style='display:none'>" + colum.TrainingID + "</td>");
            htmlTable.Append("<td>" + colum.TrainingNumber + "</td>");
            htmlTable.Append("<td class='text-center'> <a id='btnAdd' style='cursor:pointer;' class='list-icons-item text-primary-600' data-toggle='modal' data-backdrop='static' data-keyboard='false' data-target='#modal_form_horizontal' onclick='BindData(this);'><i class='icon-pencil7 mr-1'></i></a></td>");
            htmlTable.Append("</tr>");
        }
        htmlTable.Append("</tbody>");
        htmlTable.Append("</table>");

        PlaceHolderTable.Controls.Add(new Literal { Text = htmlTable.ToString() });
    }
}

<div id="modal_form_horizontal" class="modal fade">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header bg-info">
                <h5 class="modal-title">Add/Update Record</h5>
                <button type="button" class="close" data-dismiss="modal">&times;</button>&nbsp;
            </div>
            <div class="form-horizontal">
                <div class="modal-body">
                    <div class="row">
                        <div class="col-lg-6">
                            <div class="form-group">
                                <label>State</label>&nbsp;<span style="color: red">*</span>
                                <asp:DropDownList ID="ddlState" class="form-control" runat="server" required="true">
                                    <asp:ListItem Value="">Select State</asp:ListItem>
                                </asp:DropDownList>
                            </div>
                        </div>
                    </div>
                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-link" data-dismiss="modal">Close</button>
                </div>
            </div>
        </div>
    </div>
</div>

Thanks