A First Chance Exception Of Type 'System.Data.SqlClient.SqlException' Occurred In System.data.dll

Hi,

I've written this code multiple times now. But for the first time i get an error at the line underlined. My procedure runs perfectly when i execute it through Sql Query analyzer.

plzz help.. Its urgent and am unable to find the reason for this error "A first chance exception of type 'System.Data.SqlClient.SqlException' occurred in system.data.dll"

Thanks !SqlConnection conn = new SqlConnection(DbConnectionString);
conn.Open();
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "dbo.rqryTradesPRR";
cmd.Parameters.Add("@COBDate",SqlDbType.DateTime).Value = "2002-10-31 00:00:00.000" ;
SqlDataReader reader = cmd.ExecuteReader();
while(reader.Read())
{
// have written something here

}

 Thanks in advance !