This method is called by the System.Web.Security.Membership class to retrieve a user name from the Active Directory data store based on the e-mail address for the user.

If more than one user in the membership data store has the same e-mail address, the first user name encountered is returned. You can set the requiresUniqueEmail attribute of the membership element to true in the application configuration file to ensure that each e-mail address in the database is unique.

Leading and trailing spaces are trimmed from the email parameter value. If the e-mail address is empty after trimming, an ArgumentException is thrown. If the e-mail address is null, all user names in the Active Directory data store are searched, and the first user name is returned.

We recommend that you do not enable searching on production systems until you have confirmed that the search queries issued by the System.Web.Security.ActiveDirectoryMembershipProvider class do not adversely impact your directory server's performance.

Since the System.Web.Security.ActiveDirectoryMembershipProvider class is designed for a stateless Web environment, it is unable to use the paging optimizations exposed by the underlying System.DirectoryServices APIs. This means that paging operations during searches against large directories are very expensive and should be avoided. Search operations are always issued against the directory server configured in the connection string, or an automatically selected server in the case of a connection string pointing at a domain. The provider does not use a global catalog for its search methods.

The provider uses a subtree search starting at the search point specified in the connection string. See the System.Web.Security.ActiveDirectoryMembershipProvider class topic for more information about connection strings.

Namespace: System.Web.Security
Assembly: System.Web (in System.Web.dll)
Assembly Versions: 2.0.0.0
Since: .NET 2.0