How to read a dataset with multiple tables using a sql query expression in c#

1) I have a XML file that can have 2 or more tables and there are relations between them. >> use the file [login to view URL] as example; 2) I read this XML file that filled a dataset with all the tables and relations >> see example below: var xmlfilename = @[login to view URL]() + [login to view URL](); DataSet ds = new DataSet(); [login to view URL](xmlfilename, [login to view URL]); 3) Now I need to read some fields from this dataset that was selected by the user. >> example: ProductName, CategoryName, UnitPrice *The user can also apply filters and groupping those columns 4) The fields selected can be stored in a list, and I need to read them doing something like this: >> example: List<UserFields> UserFieldsList = new List<UserFields>(); datatable result = readxmldata(ds, UserFieldsList); 5) The application today allow the user to select columns from any table. It's working for any datasource where I can apply a sql query expression. So... instead to use a List, it's also possible to use a sql query expression as example below: >>> see the file [login to view URL] as example 6) the final result is a data table with the 3 columns selected by the user: ProductName, CategoryName, UnitPrice according to the filters and grouppings informed by the user. 7) I did a lot of researchs and I what I know until now is that one solution is to use SqlBulkCopy to transfer the tables to a sql database and them read from it using a sql query expression... so... this solution I already know... I want to know how to read direct from the xml file without store the data anywhere else. If more especification is needed before apply the job please contact me.