Simple.Data Many-to-many Issues - asp.net-mvc-3

Question

So I'm working through a simplified example of my hoped-for database that has the following tables:
Contractors: Id, ContractorName
Types: Id, TypeName
CoverageZips: ContractorId, Zip
TypesForContractors: ContractorId, TypeId
where contractors can have many zips and types and types and zips can have many contractors (many-to-many).
I'm trying to:
do a search for contractors in a certain zip code
then load the types for those contractors.
The SQL for the first part would probably look like:
SELECT * FROM dbo.Contractors WHERE Id IN
(SELECT ContractorId FROM dbo.CoverageZips WHERE Zip = 12345)
Here's what I have for the first part in Simple.Data. It's working, but I feel like I'm missing some of the beauty of Simple.Data...
List<int> contractorIds = new List<int>();
foreach(var coverage in _db.CoverageZips.FindAllByZip(zip)) {
contractorIds.Add((int)coverage.ContractorId);
}
var contractors = new List<dynamic>();
if (contractorIds.Count > 0) {
contractors = _db.Contractors.FindAllById(contractorIds).ToList<dynamic>();
}
return contractors;
That's working ok until I try part 2:
public dynamic GetAllForZip(int zip) {
List<int> contractorIds = new List<int>();
foreach(var coverage in _db.CoverageZips.FindAllByZip(zip)) {
contractorIds.Add((int)coverage.ContractorId);
}
var contractors = new List<dynamic>();
if (contractorIds.Count > 0) {
contractors = _db.Contractors.FindAllById(contractorIds).ToList<dynamic>();
}
foreach (var contractor in contractors) {
// Exception occurs here on second iteration
// even though the second contractor was originally in the contractors variable
contractor.types = GetTypesForContractor((int)contractor.Id);
}
return contractors;
}
public dynamic GetTypesForContractor(int id) {
var types = new List<dynamic>();
if (id > 0) {
List<int> typeIds = new List<int>();
foreach (var typeForContractor in _db.TypesForContractor.FindAllByContractorId(id)) {
typeIds.Add((int)typeForContractor.TypeId);
}
if (typeIds.Count > 0) {
types = _db.ContractorTypes.FindAllById(typeIds).ToList<dynamic>();
}
}
return types;
}
I set a breakpoint and everything works ok for the first iteration showing , but is failing on the second with the following exception:
Index was out of range. Must be non-negative and less than the size of the collection.
tl;dr
I'm not sure how to properly use many-to-many relationships with Simple.Data and something weird is happening when I try my method more than once

Answer 1

I don't know what's happening with that exception and will investigate today.
You are missing some beauty, though. Assuming you have referential integrity configured on your database (which of course you do ;)), your methods can be written thus:
public dynamic GetAllForZip(int zip) {
var contractors = _db.Contractors
.FindAll(_db.Contractors.ContractorZips.Zip == zip)
.ToList();
foreach (var contractor in contractors) {
contractor.Types = GetTypesForContractor((int)contractor.Id);
}
return contractors;
}
public dynamic GetTypesForContractor(int id) {
return _db.ContractorTypes
.FindAll(_db.ContractorTypes.TypesForContractor.ContractorId == id)
.ToList();
}
Update!
As of 1.0.0-beta3, eager-loading across many-to-many joins is supported, so now you can do this:
public dynamic GetAllForZip(int zip) {
return _db.Contractors
.FindAll(_db.Contractors.ContractorZips.Zip == zip)
.With(_db.Contractors.TypesForContractor.ContractorTypes.As("Types"))
.ToList();
}
And that executes as a single SQL select to make your DBA happy like rainbow kittens.