Creating an EF4 Context in One Way

Question

I have many ways:

public IEnumerable<Director> GetAllDirectors() { using (var dbContext = new BodModelContainer()) { return dbContext.Members.OfType<Director>().ToList(); } } 

.. or that..

  public Member GetMemberById(int memberId) { using(var dbContext = new BodModelContainer()) { return dbContext.Members.Find(new[] {memberId}); } } 

or what:

  public SomeType GetOrDoSomethingWithDbBySomethingElse(T1 t1var, T2, T2 var, ...) { using(var dbContext = new BodModelContainer()) { return dbContext.SomeType.DoSomething(); } } 

So, I want to reorganize all these methods like this:

  // create db context here public void InDb(Func<BodModelContainer, out SomeGenericType???> workingWithDb) { using(var dbContext = new BodModelContainer()) { workingWithDb(dbContext); } } // using it like public Member GetMemberById(int memberId) { InDb((dbContext) => { return dbContext.Members.Find(new[] { memberId }); }); } 

Question How to make such a general InDb method that there is SomeGenericType???

Answer 1

The actual problem, apparently, is that you cannot figure out how to set the return type to Func<> . To be able to do this in general, you will need to make InDb a generic type as well.

 public TRet InDb<TRet>(Func<BodModelContainer, TRet> workingWithDb) { TRet ret = default(TRet); using (var dbContext = new BodModelContainer()) { ret = workingWithDb(dbContext); } return ret; } public Member GetMemberById(int memberId) { return InDb(dbContext => { return dbContext.Members.Find(new[] { memberId }); }); } 

It should work (all code is untested here) or using anonymous methods you can have a local variable and make .Net do all the unpleasant work.

 public void InDb(Action<BodModelContainer> workingWithDb) { using (var dbContext = new BodModelContainer()) { workingWithDb(dbContext); } } public Member GetMemberById(int memberId) { Member member; InDb(dbContext => { member = dbContext.Members.Find(new[] { memberId }); }); return member; } 

Of course, that’s all said, I don’t know if this level of redirection / abstraction is useful - you make it a little more complicated with a small tangible gain (if any). If there is not much work to configure and break the dbContext used in InDb , I don't think this is very useful.