Mapping string to List<string> and vice versa using Automapper

There is something similar to your questiong here, please can you check this out AutoMapper: Collection to Single string Property

PS: This is an example for mapping collection to single string property probably your example should look like below;

Mapper.CreateMap<User, UserEditViewModel>()
    .ForMember(dest => dest.Roles,
    m => m.MapFrom(src => src.Role.Split(',').ToList()));

And mapping the instances like below;

User myUser = new User();
myUser.Role = "r1,r2,r3,r4,r5";
myUser.UserID = 1;
myUser.Username = "MyUserName";

UserEditViewModel result = Mapper.Map<UserEditViewModel>(myUser);

2020 Edit: Since Expression.Call API does not support optional parameter and you should Replace src.Role.Split(',') with src.Role.Split(',', System.StringSplitOptions.None) or src.Role.Split(',', System.StringSplitOptions.RemoveEmptyEntries)