Updating array

[tsubasa]

I have an array that is in C# using the .Net framwork and I have the code to delete items from the array, but I am trying to figure out how to update an item in the array.

 
public DataSet GetDataSetCar()
    {
        if (Session["car"] == null)
        {
            DataSet ds = new DataSet();
            DataColumn colID = new DataColumn("ID_Product", System.Type.GetType("System.Int32"), "");
            DataTable dt = new DataTable("Car");
            dt.Columns.Add(colID);
            dt.Columns.Add("Name_Product", System.Type.GetType("System.String"), "");
            dt.Columns.Add("Quantity", System.Type.GetType("System.Int32"), "");
            dt.Columns.Add("Value", System.Type.GetType("System.Double"), "");
            dt.Columns.Add("SubTotal", System.Type.GetType("System.Double"), "Quantity*Value");
            dt.Columns.Add("Total", System.Type.GetType("System.Double"), "SUM(SubTotal)");
            //key field
            DataColumn[] keys = new DataColumn[1];
            keys[0] = colID;
            dt.PrimaryKey = keys;
            ds.Tables.Add(dt);
            Session["car"] = ds;
            return ds;
        }
        else
        {
            return (Session["car"] as DataSet);
        }
    }

Kind Regards,

-Tsubasa