How to approach refactoring a class? (VB.Net) - vb.net

Question

I recently started a project and needed to do some integration with LDAP via DirectoryServices. I've done this in other apps so I went into one of them to see how I did it -- why reinvent the wheel right? Well, while this wheel works, it was developed years ago and kinda smells (it's wooden, firmly attached to the previous vehicle, hard to repair and produces a potentially bumpy ride).
So I thought to myself, this is the perfect time to refactor this puppy and make it more portable, reusable, reliable, easier to configure etc. Now that's fine and dandy, but then I started feeling a tad overwhelmed regarding to where to start. Should it be a separate library? How should it be configured? Should it use IoC? DI?
So my [admittedly subjective] question is this -- given a relatively small, but quite useful class like the one below, what is a good approach to refactoring it? What questions do you ask and how do you decide what to implement or not implement? Where do you draw the line regarding configuration flexibility?
[Note: Please don't bash this code too much okay? It was written a long time ago and has functioned perfectly well baked into an in house application.]
Public Class AccessControl
Public Shared Function AuthenticateUser(ByVal id As String, ByVal password As String) As Boolean
Dim path As String = GetUserPath(id)
If path IsNot Nothing Then
Dim username As String = path.Split("/")(3)
Dim userRoot As DirectoryEntry = New DirectoryEntry(path, username, password, AuthenticationTypes.None)
Try
userRoot.RefreshCache()
Return True
Catch ex As Exception
Return False
End Try
Else
Return False
End If
End Function
Private Shared Function GetUserPath(ByVal id As String) As String
Dim root As DirectoryEntry = New DirectoryEntry("LDAP://XXXXX/O=YYYY", String.Empty, String.Empty, AuthenticationTypes.None)
Dim searcher As New DirectorySearcher
Dim results As SearchResultCollection
Dim result As SearchResult
Try
With searcher
.SearchRoot = root
.PropertiesToLoad.Add("cn")
.Filter = String.Format("cn={0}", id)
results = .FindAll()
End With
If results.Count > 0 Then
result = results(0)
Return result.Path.ToString()
Else
Return Nothing
End If
Catch ex As Exception
Return Nothing
End Try
End Function
Public Shared Function GetUserInfo(ByVal id As String) As UserInfo
Dim root As DirectoryEntry = New DirectoryEntry("LDAP://XXXXX/O=YYYY", String.Empty, String.Empty, AuthenticationTypes.None)
Dim searcher As New DirectorySearcher
Dim results As SearchResultCollection
Dim props() As String = {"id", "sn", "mail", "givenname", "container", "cn"}
Try
With searcher
.SearchRoot = root
.PropertiesToLoad.AddRange(props)
.Filter = String.Format("cn={0}", id)
results = .FindAll()
End With
If results.Count > 0 Then
Dim properties As PropertyCollection = results(0).GetDirectoryEntry().Properties
Dim user As New UserInfo(properties("id").Value)
user.EmailAddress = properties("mail").Item(0).ToString
user.FirstName = properties("givenname").Item(0).ToString
user.LastName = properties("sn").Item(0).ToString
user.OfficeLocation = properties("container").Item(0).ToString
Return user
Else
Return New UserInfo
End If
Catch ex As Exception
Return Nothing
End Try
End Function
Public Shared Function IsMemberOfGroup(ByVal id As String, ByVal group As String) As Boolean
Dim root As DirectoryEntry = New DirectoryEntry("LDAP://XXXXX/O=YYYY", String.Empty, String.Empty, AuthenticationTypes.None)
Dim searcher As New DirectorySearcher
Dim results As SearchResultCollection
Dim result As SearchResult
Dim props() As String = {"cn", "member"}
Try
With searcher
.SearchRoot = root
.PropertiesToLoad.AddRange(props)
.Filter = String.Format("cn={0}", group)
results = .FindAll()
End With
If results.Count > 0 Then
For Each result In results
Dim members As PropertyValueCollection = result.GetDirectoryEntry().Properties("member")
Dim member As String
For i As Integer = 0 To members.Count - 1
member = members.Item(i).ToString
member = member.Substring(3, member.IndexOf(",") - 3).ToLowerInvariant
If member.Contains(id.ToLowerInvariant) Then Return True
Next
Next
End If
Return False
Catch ex As Exception
Return False
End Try
End Function
Public Shared Function GetMembersOfGroup(ByVal group As String) As List(Of String)
Dim groupMembers As New List(Of String)
Dim root As DirectoryEntry = New DirectoryEntry("LDAP://XXXXX/O=YYYY", String.Empty, String.Empty, AuthenticationTypes.None)
Dim searcher As New DirectorySearcher
Dim results As SearchResultCollection
Dim result As SearchResult
Dim props() As String = {"cn", "member"}
Try
With searcher
.SearchRoot = root
.PropertiesToLoad.AddRange(props)
.Filter = String.Format("cn={0}", group)
results = .FindAll()
End With
If results.Count > 0 Then
For Each result In results
Dim members As PropertyValueCollection = result.GetDirectoryEntry().Properties("member")
Dim member As String
For i As Integer = 0 To members.Count - 1
member = members.Item(i).ToString
member = member.Substring(3, member.IndexOf(",") - 3).ToLowerInvariant
groupMembers.Add(member)
Next
Next
End If
Catch ex As Exception
Return Nothing
End Try
Return groupMembers
End Function
End Class
Clarifications:
- there is a separate class for user (simple poco)
- there isn't a group class since all that's used right now is the list of ids, could be useful to add though

Answer 1

Here is an example of a refactored code sample:
Public Class AccessControl
Public Shared Function AuthenticateUser(ByVal id As String, ByVal password As String) As Boolean
Dim path As String
Dim username As String
Dim userRoot As DirectoryEntry
path = GetUserPath(id)
If path.Length = 0 Then
Return False
End If
username = path.Split("/")(3)
userRoot = New DirectoryEntry(path, username, password, AuthenticationTypes.None)
Try
userRoot.RefreshCache()
Return True
Catch ex As Exception
' Catching Exception might be accepted way of determining user is not authenticated for this case
' TODO: Would be better to test for specific exception type to ensure this is the reason
Return False
End Try
End Function
Private Shared Function GetUserPath(ByVal id As String) As String
Dim results As SearchResultCollection
Dim propertiesToLoad As String()
propertiesToLoad = New String() {"cn"}
results = GetSearchResultsForCommonName(id, propertiesToLoad)
If results.Count = 0 Then
Return String.Empty
Else
Debug.Assert(results.Count = 1)
Return results(0).Path
End If
End Function
Public Shared Function GetUserInfo(ByVal id As String) As UserInfo
Dim results As SearchResultCollection
Dim propertiesToLoad As String()
propertiesToLoad = New String() {"id", "sn", "mail", "givenname", "container", "cn"}
results = GetSearchResultsForCommonName(id, propertiesToLoad)
If results.Count = 0 Then
Return New UserInfo
End If
Debug.Assert(results.Count = 1)
Return CreateUser(results(0).GetDirectoryEntry().Properties)
End Function
Public Shared Function IsMemberOfGroup(ByVal id As String, ByVal group As String) As Boolean
Dim allMembersOfGroup As List(Of String)
allMembersOfGroup = GetMembersOfGroup(group)
Return allMembersOfGroup.Contains(id.ToLowerInvariant)
End Function
Public Shared Function GetMembersOfGroup(ByVal group As String) As List(Of String)
Dim results As SearchResultCollection
Dim propertiesToLoad As String()
propertiesToLoad = New String() {"cn", "member"}
results = GetSearchResultsForCommonName(group, propertiesToLoad)
Return ConvertMemberPropertiesToList(results)
End Function
Private Shared Function GetStringValueForPropertyName(ByVal properties As PropertyCollection, ByVal propertyName As String) As String
Return properties(propertyName).Item(0).ToString
End Function
Private Shared Function CreateUser(ByVal userProperties As PropertyCollection) As UserInfo
Dim user As New UserInfo(userProperties("id").Value)
With user
.EmailAddress = GetStringValueForPropertyName(userProperties, "mail")
.FirstName = GetStringValueForPropertyName(userProperties, "givenname")
.LastName = GetStringValueForPropertyName(userProperties, "sn")
.OfficeLocation = GetStringValueForPropertyName(userProperties, "container")
End With
Return user
End Function
Private Shared Function GetValueFromMemberProperty(ByVal member As String) As String
Return member.Substring(3, member.IndexOf(",") - 3).ToLowerInvariant
End Function
Private Shared Function ConvertMemberPropertiesToList(ByVal results As SearchResultCollection) As List(Of String)
Dim result As SearchResult
Dim memberProperties As PropertyValueCollection
Dim groupMembers As List(Of String)
groupMembers = New List(Of String)
For Each result In results
memberProperties = result.GetDirectoryEntry().Properties("member")
For i As Integer = 0 To memberProperties.Count - 1
groupMembers.Add(GetValueFromMemberProperty(memberProperties.Item(i).ToString))
Next
Next
Return groupMembers
End Function
Private Shared Function GetSearchResultsForCommonName(ByVal commonName As String, ByVal propertiesToLoad() As String) As SearchResultCollection
Dim results As SearchResultCollection
Dim searcher As New DirectorySearcher
With searcher
.SearchRoot = GetDefaultSearchRoot()
.PropertiesToLoad.AddRange(propertiesToLoad)
.Filter = String.Format("cn={0}", commonName)
results = .FindAll()
End With
Return results
End Function
Private Shared Function GetDefaultSearchRoot() As DirectoryEntry
Return New DirectoryEntry("LDAP://XXXXX/O=YYYY", String.Empty, String.Empty, AuthenticationTypes.None)
End Function
End Class
I think you can ever take this further by extracting constants, etc, but this removes most of the duplication, etc. Let me know what you think.
Way, too late, I realize... but also wanted to address some of the questions you asked as well. See http://chrismelinn.wordpress.com/2011/06/18/questions-before-refactoring-2/

Answer 2

I believe it's important to modify the exception handling as well. The pattern I see in the methods above is:
Try
...
Catch ex As Exception
Return False
End Try
The code above is essentially hiding (swallowing) its exceptions. This may have been implemented initially because certain types of exceptions were thrown as a result of the user not being found, and returning False or Nothing was probably appropriate. However, you may been getting other types of exceptions in your application which you may never know about (e.g. OutOfMemoryException, etc).
I would suggest catching only specific types of exceptions that you may want to legitimately return false/Nothing. For others, let the exception bubble up, or log it at a minimum.
For other tips on exception handling, read this helpful post.

Answer 3

The first thing I would do is remove any duplication. Strip out common functionality in to separate methods.
Also, think along the lines of every class should have a single role/responsibility - you might want to create separate User and Group classes.
There is a catalog of common refactorings here:
http://www.refactoring.com/catalog/index.html
You should only really consider Inversion of Control if you wish to swap in different classes for testing reasons etc...

Answer 4

It might not be the most significant refactoring, but I am a big fan of the early return. So, for instance, where you have:
If results.Count > 0 Then
Dim properties As PropertyCollection = results(0).GetDirectoryEntry().Properties
Dim user As New UserInfo(properties("id").Value)
user.EmailAddress = properties("mail").Item(0).ToString
user.FirstName = properties("givenname").Item(0).ToString
user.LastName = properties("sn").Item(0).ToString
user.OfficeLocation = properties("container").Item(0).ToString
Return user
Else
Return New UserInfo
End If
I would use, instead:
If results.Count == 0 Then Return New UserInfo
Dim properties As PropertyCollection = results(0).GetDirectoryEntry().Properties
Dim user As New UserInfo(properties("id").Value)
user.EmailAddress = properties("mail").Item(0).ToString
user.FirstName = properties("givenname").Item(0).ToString
user.LastName = properties("sn").Item(0).ToString
user.OfficeLocation = properties("container").Item(0).ToString
Return user
Indentation implies complexity, and there isn't enough complexity in the special handling of the empty result case to warrant 8 lines of indentation. There is a point at which removing indentation can actually hide real complexity, so don't push this rule too hard, but for the code presented, I'd definitely use the early return.

Answer 5

The first thing that immediately jumps out at me is that there's a lot of functions involving users that don't seem to be associated with the user class you have created.
I would try some of the following approaches:
Add the following to the user class:
Path
Authenticate(string password) - this could be a static method, not sure of the use cases here.
Groups - I would also recommend creating an actual domain object for groups. It could have a collection of users as a property to start with.