Adds the specified users to the specified role.
Assembly: System.Web (in System.Web.dll)
roleName is nullptr.
One of the elements in usernames is nullptr.
roleName is an empty string or contains a comma (,).
One of the elements in usernames is an empty string or contains a comma (,).
usernames contains a duplicate element.
Role management is not enabled.
The method calls the default role provider to associate the specified users with the specified role at the data source.
If your application uses the SqlRoleProvider class, the database updates that are performed during the call to the AddUsersToRoles method are made within a transaction. If an error is encountered, such as a user name that is already in a specified role, the transaction is rolled back and no updates are performed.
User names and role names cannot contain commas.