How to implement Active Directory resolution with SAML authentication in SharePoint 2010?

If you configured SharePoint web application in claims mode with federated authentication (with an external STS such as ADFS), you certainly remarked that OOB SharePoint does not offer any search or resolution against Active Directory. And you certainly thought it would be really nice to have it.

Well, there are good reasons to explain this: since users authenticate in an external STS, SharePoint cannot assume if the users authenticated within the organization, or outside, and it also doesn’t know if users authenticated in a LDAP or in a totally different login system such as a SQL DB.

Fortunately, SharePoint gives the possibility for developers to  create a claim provider that implements this, and I recently published mine on codeplex: https://ldapcp.codeplex.com/. It integrates easily with existing environments, does not mess up anything and is available for free with the source code!