Iterating over SearchResultCollection is Very Slow - asp.net

Question

I'm running an LDAP query that returns multiple entries and stores them inside a SearchResultCollection. I'm iterating over the SearchResultCollection like so:
// results is my SearchResultCollection object
foreach (SearchResult sr in results)
{
... do things to each SearchResult in here ...
}
This seems like the most logical way to do this, but loop is incredibly slow. When I step through the loop with the debugger, I find that it's the very first step of initializing the foreach loop that takes the time - the actual iterations are instantaneous.
In addition, when I view the contents of the SearchResultCollection while debugging, the watch takes just as long to load the contents of the variable.
I have a theory that the SearchResultCollection doesn't actually contain complete SearchResult objects, but rather references to entries in the Active Directory server that are then individually fetched when I iterate over the SearchResultCollection object. Can anyone confirm this theory? And is there a better (faster) way to fetch a set of LDAP entries?

Answer 1

I suffered from the same problem and the methodology in the post below was much quicker then my own:
http://msdn.microsoft.com/en-us/library/ms180881(v=vs.80).aspx
... to answer you question yes it seems as if you try to process the entries directly while still in the loop by using something like:
If Not UserAccount.GetDirectoryEntry().Properties("sAMAccountName").Value Is Nothing Then sAMAccountName = UserAccount.Properties("sAMAccountName")(0).ToString()
... this has a drastic impact on performance, you can get around this by adding the collection to a Dictionary within the loop and then processing the dictionary:
Dim searchResult As SearchResult
Dim dictLatestLogonDatesTemp As New Dictionary(Of String, Date)
SearchResults1 = mySearcher.FindAll()
For Each searchResult In SearchResults1
Dim propertyKey,sAMAccountName As String
Dim dteLastLogonDate As Date = Nothing
For Each propertyKey In searchResult.Properties.PropertyNames
Dim valueCollection As ResultPropertyValueCollection = searchResult.Properties(propertyKey)
For Each propertyValue As Object In valueCollection
If LCase(propertyKey) = LCase("sAMAccountName") Then sAMAccountName = propertyValue
If LCase(propertyKey) = LCase("lastLogon") Then dteLastLogonDate = Date.FromFileTime(propertyValue)
Next propertyValue
Next propertyKey
If sAMAccountName <> Nothing Then dictLatestLogonDatesTemp.Add(sAMAccountName, dteLastLogonDate)
Next searchResult
It is a bit restrictive bacause a dictionary ony has two entries but you can comma seperate other values or use a dictionary of values in the dictionary:
Dim tempDictionary As Dictionary(Of String, Dictionary(Of String, String))
Hope this helps someone!

Answer 2

I would like to submit that adding them to a datatable also works very well and allows for more properties than a dictionary. I went from iterating 2000 users in the searchresultscollection taking almost 2 minutes to less that 1-2 seconds. Hope this helps others.
Private Sub getAllUsers()
Dim r As SearchResultCollection
Dim de As DirectoryEntry = New DirectoryEntry(GetCurrentDomainPath)
Dim ds As New DirectorySearcher(de)
ds.SearchScope = SearchScope.Subtree
ds.PropertiesToLoad.Add("name")
ds.PropertiesToLoad.Add("distinguishedName")
ds.PropertiesToLoad.Add("objectSID")
ds.Filter = "(&(objectCategory=person)(objectClass=user))" '(!userAccountControl:1.2.840.113556.1.4.803:=2) not disabled users
PleaseWait.Status("Loading Users...")
Application.DoEvents()
r = ds.FindAll()
Dim dt As New DataTable
dt.Columns.Add("Name")
dt.Columns.Add("SID")
For Each sr As SearchResult In r
Dim SID As New SecurityIdentifier(CType(sr.Properties("objectSID")(0), Byte()), 0)
dt.Rows.Add(sr.Properties("name")(0).ToString(), SID.ToString)
Next
With lstResults
lstResults.DataSource = dt
.DisplayMember = "name"
.ValueMember = "SID"
.Items.Sort()
End With
End Sub

Answer 3

There may be some ways to decrease the response time:
restrict the scope of the search
use a more restrictive search filter
use a base object closer to the object(s) being retrieved.
see also
LDAP: Mastering Search Filters
LDAP: Programming practices
LDAP: Search Best Practices