Typed DataSet, GridView and Computed Column

[mirco]

Hi,
I have created a Typed DataSet. The DataTable is (distrimarket.DatiDT).
Then a GridView is populated. The last column is computed and it is the
difference between the previous two. I get this error: Unable to cast object
of type 'System.Data.DataRow' to type 'DataTable1Row'.
Could you tell me what is wrong please ?
protected void GridView2_RowDataBound(object sender, GridViewRowEventArgs e)
{
System.Data.DataRowView drv;
drv = (System.Data.DataRowView)e.Row.DataItem;
try{

if (e.Row.RowType == DataControlRowType.DataRow)
{
distrimarket.DatiDTRow dati = (distrimarket.DatiDTRow)drv.Row;

if (!dati.IsQta_InviatoNull() && !dati.IsQTa_ResoNull())
{
sold += dati.Qta_Inviato - dati.QTa_Reso;
e.Row.Cells[4].Text = sold.ToString();
}

}
}
catch (Exception ex)
{
string err;
err = "Description: " + ex.Message;
}
}