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Can I get more than 1000 records from a DirectorySearcher in ASP.NET?

Posted by: admin November 29, 2017 Leave a comment

Questions:

I just noticed that the return list for results is limited to 1000. I have more than 1000 groups in my domain (HUGE domain). How can I get more than 1000 records? Can I start at a later record? Can I cut it up into multiple searches?

Here is my query:

DirectoryEntry dirEnt = new DirectoryEntry("LDAP://dhuba1kwtn004");
string[] loadProps = new string[] { "cn", "samaccountname", "name", "distinguishedname" };
DirectorySearcher srch = new DirectorySearcher(dirEnt, "(objectClass=Group)", loadProps);
var results = srch.FindAll();

I have tried to set srch.SizeLimit = 2000;, but that doesn’t seem to work. Any ideas?

Answers:

You need to set DirectorySearcher.PageSize to a non-zero value to get all results.

BTW you should also dispose DirectorySearcher when you’re finished with it

using(DirectorySearcher srch = new DirectorySearcher(dirEnt, "(objectClass=Group)", loadProps))
{
    srch.PageSize = 1000;
    var results = srch.FindAll();
}

The API documentation isn’t very clear, but essentially:

  • when you do a paged search, the SizeLimit is ignored, and all matching results are returned as you iterate through the results returned by FindAll. Results will be retrieved from the server a page at a time. I chose the value of 1000 above, but you can use a smaller value if preferred. The tradeoff is: using a small PageSize will return each page of results faster, but will require more frequent calls to the server when iterating over a large number of results.

  • by default the search isn’t paged (PageSize = 0). In this case up to SizeLimit results is returned.

As Biri pointed out, it’s important to dispose the SearchResultCollection returned by FindAll, otherwise you may have a memory leak as described in the Remarks section of the MSDN documentation for DirectorySearcher.FindAll: http://msdn.microsoft.com/en-us/library/system.directoryservices.directorysearcher.findall.aspx

One way to help avoid this in .NET 2.0 or later is to write a wrapper method that automatically disposes the SearchResultCollection. This might look something like the following (or could be an extension method in .NET 3.5):

public IEnumerable<SearchResult> SafeFindAll(DirectorySearcher searcher)
{
    using(SearchResultCollection results = searcher.FindAll())
    {
        foreach (SearchResult result in results)
        {
            yield return result;        
        } 
    } // SearchResultCollection will be disposed here
}

You could then use this as follows:

using(DirectorySearcher srch = new DirectorySearcher(dirEnt, "(objectClass=Group)", loadProps))
{
    srch.PageSize = 1000;
    var results = SafeFindAll(srch);
}