Question

Using Linq I would like to return an object that contains customers and invoices they have.

I understand returning a single type from a method:

public IQueryable<customers> GetCustomers()
{
    return from c in customers
           select c;
}

But I am having trouble figuring out multiple objects:

public IQueryable<???> GetCustomersWithInvoices()
{
    return from c in customers
           from inv in c.invoices
           select new {c, ci}  // or I may specify columns, but rather not.
}

I have a feeling I am approaching this the wrong way. The goal is to call these objects from a controller and pass them up to a view, either direct or using a formViewModel class.

Answer 1

In the second case you are creating an annonymous type which has method scope. To pass an annonymous type outside the method boundary you need to change the return type to object. This however defeats the purpose of the annonymous type (as you lose the strong typing it provides) , requiring reflection to get access to the properties and their values for the said type.

If you want to maintain this structure as your return type you should create a class or struct consisting of properties to hold the customer and invoice values.