LINQ To LDAP: How Does It Work Part 1

UPDATE: Query methods have been reduced to encourage manual mapping for non-anonymous types.
UPDATE: root has been renamed to namingContext

So in my last post I had two examples showing Linq to LDAP working. I want to cover how it all works. I'll start with the interface IDirectoryContext:

public interface IDirectoryContext : IDisposable
{
    IQueryable<T> Query<T>() where T : class;
    IQueryable<T> Query<T>(SearchScope scope) where T : class;
    IQueryable<T> Query<T>(T example, string namingContext) where T : class;
    IQueryable<T> Query<T>(T example, string namingContext, string objectCategory) where T : class;
    IQueryable<T> Query<T>(T example, SearchScope scope, string namingContext) where T : class;
    IQueryable<T> Query<T>(T example, SearchScope scope, string namingContext, string objectCategory) where T : class;
}

The available parameters:

• example: This as an anonymous object that can be used for auto mapping. In my previous post my anonymous object looked like this:
  

  var example = new {DistinguishedName = "", Cn = ""};
     

  All you need is to specify a name and a value so the compiler can infer the type. Here's an example with more properties:
  

  var example =
      new
          {
              DistinguishedName = "",
              Cn = "",
              WhenCreated = default(DateTime),
              ObjectGuid = default(Guid),
              DirectReports = default(string[])
          };
     

  Auto mapped properties must have names that match the directory attribute name. Casing does not matter.
  
• scope: This determines the depth at which the search is performed. You can read more about search scopes here. I always default to a subtree scope if you don't specify one.
  
• namingContext: This is the place in the directory from which you want to start your search. You can make it the root of the directory "DC=Northwind,DC=local" or you can go deeper "CN=Users,CN=Employees,DC=Northwind,DC=local". You'll notice that if you query by example, you must always specify the naming context. I do this because auto mapping cannot infer the naming context.
  
• objectCategory: This is an LDAP attribute you can specify to improve searching performance. You may be wondering why I use objectCategory instead of objectClass. It boils down to objectCategory being single valued and objectClass being multivalued so searching by objectCategory is faster. You can read more about it here.