Question

I’m new to LINQ, I’ve used LINQ to SQL to link to two tables, it does return data, which is cool. What I’m trying to understand is what datatype is being returned and how do I work with this datatype?

I’m used to dealing with datatables. Are we throwing out datatables (and all the other ADO.Net object like rows, datasets etc.) now if using LINQ? If so, what are we replacing that with and how can I use it to do everything I did before with datatables? Also–does it make sense to replace datables, was there a deficiency with them?

Here is some code:

protected IEnumerable<string> GetMarketCodes() {     LINQOmniDataContext db = new LINQOmniDataContext();      var mcodes = from p in db.lkpMarketCodes                      orderby 0                     select p;      return (IEnumerable<string>) mcodes; } 

This code does currently return data (I can see it in debug), but errors at the ‘return’ line, because apparently my datatype is not IEnumerables, which was my best guess. So, one thing I’d like to understand as well is what datatype is my data being put into and how to return it to the calling function.

Answer 1

It is returning an IQueryable<lkpMarketCode>, assuming that that lkpMarketCode is the type of data in db.lkpMarketCodes. If you want the strings, you need to select p.SomeProperty;, not just select p;.

You shouldn’t need to cast (since IQueryable<T> implements IEnumerable<T>); it should also tell you this if you hover on mcodes.