Gridview Control Coding

Hii,
You can do 1 thing in simple way,

1)In case of Update click in a gridview, first of all set the CommandArgument property of button with the primarykeyId

Like,
>
2) OnRowCommand event of grid, check for the CommandName="UpdateMyData"
if(e.CommandName == "UpdateMyData")
{
        string id = e.CommandArgument.toString();
        Response.Redirect("InsertPage.aspx?id=" + id);
}
3)In InsertPage.aspx, on page_load event check for querystring value and load the data
if(Request.QueryString["id"] != null)
{
        LoadData();
        string mode= "update";
}

I hope this will help you to solve your problem. If you think it as helpful please mark it Like.