Retrieving the data from database using webservice dataset that time display the error

sir,

Retrieving the data from database using webservice dataset that time display the error
there is no row at position 0.

My code
localhost.WebService s = new localhost.WebService();

DataSet ds = s.serverstatuspasient1(nymbleticket, Servername);

string sts = ds.Tables[0].Rows[0].ItemArray[0].ToString();

regard
sekar.c

Regards
Sekar.c