You can use a PrincipalSearcher and a "query-by-example" principal to do your searching:
// LDAP string to define your OU
string ou = "OU=Sales,DC=YourCompany,DC=com";
// set up a "PrincipalContext" for that OU
using (PrincipalContext ctx = new PrincipalContext(ContextType.Domain, "Yourcompany.com", ou))
{
// define the "query-by-example" user (or group, or computer) for your search
UserPrincipal qbeUser = new UserPrincipal(ctx);
// set whatever attributes you want to limit your search for, e.g. Name, etc.
qbeUser.Surname = "Smith";
// define a searcher for that context and that query-by-example
using (PrincipalSearcher searcher = new PrincipalSearcher(qbeUser))
{
foreach (Principal p in searcher.FindAll())
{
// Convert the "generic" Principal to a UserPrincipal
UserPrincipal user = p as UserPrincipal;
if (user != null)
{
// do something with your found user....
}
}
}
If you haven't already - absolutely read the MSDN article Managing Directory Security Principals in the .NET Framework 3.5 which shows nicely how to make the best use of the new features in System.DirectoryServices.AccountManagement. Or see the MSDN documentation on the System.DirectoryServices.AccountManagement namespace.
Of course, depending on your need, you might want to specify other properties on that "query-by-example" user principal you create:
DisplayName (typically: first name + space + last name)
SAM Account Name - your Windows/AD account name
User Principal Name - your "username@yourcompany.com" style name
You can specify any of the properties on the UserPrincipal and use those as "query-by-example" for your PrincipalSearcher.