AutoMapper and Repository Pattern

See more:

C#

C#4.0

I am trying out AutoMapper on a Silverlight project.

I am a newbie on AutoMapper and actually just got introduced to it yesterday.

My Sample's data communication pattern goes thus: RDBM => ORM => Repository => DTO and vice versa.

Having done everything and getting to my server side WCF class for transmission to client I seem to be lacking there.

Manual Mapping:

public IEnumerable<UserPM> GetByID(int userID)
{
    var user = _repo.GetByID(userID);
    return new UserPM()
    {
        UserName = user.UserName,
        FirstName = user.FirstName
        LastName = user.LastName
    }
}

AutoMapper:

public IEnumerable<UserPM> GetByID(int userID) // Conversion error except for public IEnumerable<User> GetByID(int userID)
{
    var user = _repo.GetByID(userID);
    AutoMapper.Mapper.CreateMap<User, UserPM>();
    return user;
}

Here is the issue. I get an error saying User can not be implicitly converted to UserPM. My repository at work there. The reason
a Presentation Model is to filter your data for specific requests... Am I wrong here... Please help.