Gridview always emtpy on modal popup

I want to populate a gridview (on modal popup) based on another control. But the grid databound method is never fired. Here is my code..

 <div class="modal fade" id="ParamValueTypes" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" onclick="javascript: ClearAndClosetxt();"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
                    <h4 class="trpopupHeader" id="ParamValues">Parameters and Values</h4>
                </div>
                <div class="modal-body">
                    <asp:Button runat="server" ID="btnViewGrid" CssClass="btn btn-primary btn-xs" Text="View Grid" OnClick="btnViewGrid_Click" />                                   
                    <asp:GridView ID="ParamValuesGridView" runat="server" BorderStyle="Solid" BorderColor="#DEDFDE"
                        Width="100%" AllowSorting="True" BackColor="White" AutoGenerateColumns="false"
                        ForeColor="Black" GridLines="None" BorderWidth="1px" OnDataBound ="ParamValuesGridView_DataBound">
                        <AlternatingRowStyle BackColor="White" />
                        <EmptyDataTemplate>
                            No Records...
                        </EmptyDataTemplate>
                            <Columns>
                                <asp:TemplateField HeaderText="Parameter" Visible="true"> 
                          
                                <ItemTemplate>
                                    <asp:Label ID="lblParam" runat="server" Text='<%# Eval("Parameter") %>'></asp:Label>
                                </ItemTemplate>
                                </asp:TemplateField>
                                <asp:TemplateField HeaderText="Value" Visible="true"> 
                                <EditItemTemplate>
                                    <asp:TextBox ID="txtParamValue" runat="server" Text='<%# Eval("Value") %>' CssClass="RadioButtonList"></asp:TextBox>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="lblParamValue" runat="server" Text='<%# Eval("Value") %>'></asp:Label>
                                </ItemTemplate>
                                </asp:TemplateField>
                            </Columns>
                                                                                                                                                                       
                        </asp:GridView>                       
                </div>              
            </div>
        </div>
    </div>

.cs code:

protected void ParamValuesGridView_DataBound(object sender, EventArgs e)
        {
            GridView ParamValues = sender as GridView;
            DataTable dt = new DataTable();
            if (Session["ParametersForKeyword"] != null)
            {
                string ParameterList = Session["ParametersForKeyword"].ToString();
                String[] Parameters = ParameterList.Split(',');
                if (Parameters.Length > 0)
                {
                    dt = CreateParamValues(Parameters);
                }
                ParamValues.DataSource = dt;
            }
        }
        public DataTable CreateParamValues(string[] Params)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Parameter");
            dt.Columns.Add("Value");
            DataRow dr = null;
            for (int i = 0; i < Params.Length; i++)
            {
                dr = dt.NewRow();
                dr["Parameter"] = Params[i];
                dr["Value"] = 0;
                dt.Rows.Add(dr);
            }
            return dt;
        }