Question

My team is using Entity Framework 4.3.0 – Code Only with POCO classes as our ORM. Right now we use DBSets of Classes to access our ‘tables’

Public Property Customers As DbSet(Of Customers)

But often we are doing soft deletes based on a IsDeleted column in LINQ, and filtering our select statements accordingly:

Dim LiveCustomers =
    From C In EM.Customers
    Where C.DeleteFlag = False

What I would really like to do is, instead of writing every query to include this filter, create some lower level property (possibly at our inherited DbContext level) that provides the filtered set, while maintaining strong type.

I tried this:

Public Property Customers As DbSet(Of Customer)

Public Property Customers_Live As DbSet(Of Customer)
    Get
        Return From C In Customers
                Where C.DeleteFlag = False
    End Get
    Set(value As DbSet(Of Customer))
        Customers = value
    End Set
End Property

However that yielded me this error:

Multiple object sets per type are not supported. The object sets ‘Customers’ and ‘Customers_Live’ can both contain instances of type ‘__.Customer’.

A quick check on google yielded this promising result (How to: Query Objects with Multiple Entity Sets per Type) But after updating my Connection String, I’m still getting the same error.

  <add name="EntityManager"
       providerName="System.Data.SqlClient"
       connectionString="
          Data Source=xxxxxx;
          Initial Catalog=xxxxxx;
          User Id=xxxxxx;
          Password=xxxxxx;
          MultipleActiveResultSets=True"/>

So my question is, how could I effectively create a LINQ view that allows me to apply filtering, without impacting the upstream usage too drastically?

Answer 1

Change your property like this:

Public Property Customers As DbSet(Of Customer)

Public Property Customers_Live As IQueryable(Of Customer)
    Get
        Return From C In Customers
                Where C.DeleteFlag = False
    End Get
End Property

This is slightly different, as you won’t have things like Add() or Remove(), but for a view you typically wouldn’t expect to have that kind of functionality. If you want to add a new one, or remove one you should use the normal Customers property.