将字符串映射到列表<string>反之亦然使用 Automapper

Question

Basically I have this class which represents 1:1 with my database

public class User
{
    public int UserID { get; set; }
    public string Username { get; set; }
    public string Role { get; set; }
}

and I have this viewmodel

public class UserEditViewModel
{
    public UserEditViewModel()
    {
        Roles = new List<string>();
    }

    public int UserID { get; set; }
    [Required]
    public string Username { get; set; }
    [Required]
    public List<string> Roles { get; set; }
}

I have no idea how to map between these 2. My current setup :

Mapper.CreateMap<UserEditViewModel, User>().ReverseMap();

Answer 1

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)

Answer 2

To map a string to a collection Cihan Uygun's answer works, only to fix the error

CS0854 An expression tree may not contain a call or invocation that uses optional arguments

which is caused in later updates you should Replace src.Role.Split(',') with src.Role.Split(',', System.StringSplitOptions.None) or src.Role.Split(',', System.StringSplitOptions.RemoveEmptyEntries)

To do the reverse mapping just use src => string.Join(',', src.Roles)

Source for the error fix: https://newbedev.com/mapping-string-to-list-string-and-vice-versa-using-automapper

Answer 3

If you want to concatenate all values in your list of string you need to use string.Join . In mapper you need to use ForMember method.

From UserEditViewModel to User :

Mapper.CreateMap<User, UserEditViewModel>().ForMember(user => user.Role, opt => opt.MapFrom(userEdit => string.Join(", ", userEdit.Roles)));

From User to UserEditViewModel :

Mapper.CreateMap<UserEditViewModel, User>().ForMember(userEdit => userEdit.Roles, opt => opt.MapFrom(user => user.Role.Split(",").ToList()));

Answer 4

I think you should be able to use the AutoMapper AfterMap, something like this:

.AfterMap((src,dest) => dest.Roles.Add(src.Role))

Credit to the answer here: Map a property to a collection item