variabile locale non assegnata

[stee85]

ho un problema con l'assegnazione d una variabile.
Il codice è questo

string query_exp;
if (lblExhId.Text=="")
{
query_exp="Select ExhFrd,ExhTod,ExhPrg,ExhCmp,ExhInq,ExhLev,ExhCnt,E xhNot,ExhOwnId from Exh where ExhAnaId="+ Convert.ToInt32(Session["idana"]);
}
if(Session["prev-next"].ToString()=="next")
{
query_exp="Select ExhFrd,ExhTod,ExhPrg,ExhCmp,ExhInq,ExhLev,ExhCnt,E xhNot,ExhOwnId from Exh where ExhOwnId>"+ Convert.ToInt32(lblExhId.Text) +" and ExhAnaId="+ Convert.ToInt32(Session["idana"]);
}
if (Session["prev-next"].ToString()=="prev")
{
query_exp="Select ExhFrd,ExhTod,ExhPrg,ExhCmp,ExhInq,ExhLev,ExhCnt,E xhNot,ExhOwnId from Exh where ExhOwnId<"+ Convert.ToInt32(lblExhId.Text) +" and ExhAnaId="+ Convert.ToInt32(Session["idana"]);
}

SqlDataReader dr_exp;
SqlCommand cmd_exp=new SqlCommand(query_exp,conn);

Mi dice :
Utilizzo della varibile locale query_exp non asseganto

[stee85]

niente già risolto bastava mettere else if

grazie