Atleast you might post the code which you have tried, but i guess the issue may be you bound the datasource to Gridview on postback.
So write the code in not postback.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GridView1.Datasource = DataTable1;
GridView1.DataBind();
}
}
Just let us know the status, if not then post your code.