public string connectionString = "server=10.66.66.16;database=db;uid=sa;pwd=aa";
public static DataSet Query(string SQLString)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    SqlDataAdapter command = new SqlDataAdapter(SQLString, connection);
                    command.Fill(ds, "ds");
                }
                catch (System.Data.SqlClient.SqlException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }
string sql = "select ParentId from Tab_System_Area where AreaId=" + Aid +""; 
dataset ds=Query(sql);
string id= ds.datatables[0].rows[0]["ParentId"].tostring();

------解决方案--------------------
这不查出来了吗~
SqlConnection con = new Sqlconnection(connectionstring);
SqlCommand com = new SqlCommand(con,sql);
SqlReader reader = com.ExecuteReader();
reader里面就读出来了


------解决方案--------------------
try
               {
                   sql = "select ParentId from Tab_System_Area where AreaId=" + Aid +"";  

                   SqlCommand cmd=new SqlCommand(sql,conn);
                   cmd.Connecction.Open();
                   SqlDataReader reader = cmd.ExecuteReader();
                   
                   if (reader.Read())
                   {
                    int id = (int)reader["ParentId "];
                    
                   }
                   reader.Close();

               }
               catch (Exception ex)
               {
                   Logger.LogException(LogComponentConstants.SQLServer, ex.Message);
               }
               finally
               {
                   try
                   {
                       conn.Close();
                   }
                   catch { }
               }