Question

I’m building a DLL with several ‘master’ objects that need access to the app LINQ DataContext. The DLL will serve several projects with different dataContexts, so I need the DLL can call the object that it’s inside the EXE.

What is the best or elegant way to do it?

Edit: Clarification
Code example of what I’m trying to do:

'DLL '--- Public MustInherit Class MasterObject(Of T As Class)    Friend db As DataContext    Public Sub New()       'How do I do something like this?       db = New DataContextInTheExe()    End Sub     ...     Public MustOverride Sub Save() end class  'In the Exe '--- Public Class Order    Inherits MasterObject(Of Order)     Public Overrides Sub Save()        ...        Me.db.SubmitChanges()    End Sub end class 

Answer 1

The most appropriate way to do this is for the exe to pass the data-context to the dll, for example as a method argument to whatever the dll is doing, or as a constructor argument to whatever class (in the dll) needs it. If you have different types of data-contexts, then the type would have to be DataContext or a subclass. Extension methods (on DataContext) are one way of doing this (but not the only way).

Alternatively – in a standard ‘repository’ implementation (where the dll is the repository), it is entirely possible that the caller (the exe) doesn’t even know about the data-context – just the ICustomerRepository interface (or whatever) that the dll exposes.

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Re the edit; by this alone, it would have no way of knowing the type of data-context to create. You possibly need to either pass a data-context in, or tell it (via generics) the type of data-context; excuse my C#, but:

public abstract class MasterObject<TDataContext, TEntity>     where TDataContext : DataContext, new()     where TEntity : class {     internal TDataContext db;     public MasterObject() {         db = new TDataContext();     } } 

However, I strongly suspect that the dependency-injection route is simpler – i.e. let the caller tell us:

public abstract class MasterObject<TEntity>     where TEntity : class {     internal DataContext db;     public MasterObject(DataContext db) {         this.db = db;     } }