foreach (GridViewRow item in GridView1.Rows)
{
string str= item.Cells[i].Text;
}
Or
you can add a ItemTemplate to Rows and add a Button to Template.Add Bind the parameter "CommandName " and "CommandArgument".
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "Detail")
{
e.CommandArgument.ToString();
}
}