How do I add data that is in memory to a dataset so that I can execute sql queries on it in order to return something that I can manage in a while or foreach loop?

Basically I have a file with data, that I'd like to be able to execute sql on to sort it. Something along these lines

while(not EOF)
{
Read data from file
add data to dataset
}

execute query on dataset

foreach row in dataset
{
create a treeview node for row.field
}

This should be simple.