I want to add rows to child grid on a button click

by using the add button im trying to add rows to child grid view like this

protected void Add(object sender, EventArgs e)

{

GridViewRow row = (GridViewRow)((ImageButton)sender).Parent.Parent;

GridView gv = (GridView)row.FindControl("Gridview1");

DataTable dt = new DataTable();

DataRow dr = null;

dt.Columns.Add(new DataColumn("EmployeeKey", typeof(int)));

dt.Columns.Add(new DataColumn("tbName", typeof(string)));

dt.Columns.Add(new DataColumn("tbAmount", typeof(string)));

dt.Columns.Add(new DataColumn("tbEffDate", typeof(string)));

dr = dt.NewRow();

dr["EmployeeKey"] = gr.Cells[1].Text;

dr["tbName"] = string.Empty;

dr["tbAmount"] = string.Empty;

dr["tbEffDate"] = string.Empty;

dt.Rows.Add(dr);

ViewState["CurrentTable"] = dt;

gv.DataSource = dt;

gv.DataBind();

}

but its not working out child grid is not updating with rows can any body help

here is the source code

ShowHeader="true" DataKeyNames="EmployeeKey" AllowPaging="true"

PageSize="5" ForeColor="#333333" GridLines="None"

onpageindexchanging="gvEmpDetails_PageIndexChanging"

Width="80%" OnRowDataBound="gvEmpDetails_RowDataBound" OnRowCommand="gvEmpDetails_RowCommand" >

<%# Container.DataItemIndex + 1 %>

Name

Amount

Effective Date

ForeColor="#333333" GridLines="None" AutoGenerateColumns="false">