AutoMapper Remapping the Object based on Nested Values

Question

I am currently fetching a list of object from the database and would like to return it in a certain way from my ASP.Net Web API with Automapper. My Object currently looks like this after fetching it from the database:

[
    {
        "id": 1,
        "dropdown": "Country",
        "value": "Germany"
    },
    {
        "id": 2,
        "dropdown": "Country",
        "value": "United States"
    },
    {
        "id": 5,
        "dropdown": "Type",
        "value": "Lead"
    },
    {
        "id": 6,
        "dropdown": "Type",
        "value": "Account"
    },
    {
        "id": 7,
        "dropdown": "Type",
        "value": "Reseller"
    },
    {
        "id": 8,
        "dropdown": "Type",
        "value": "Distributor"
    }
]

But I would like it to look like this:

[{
    "Countries": [{
        "id": 1,
        "value": "Germany"
      },
      {
        "id": 2,
        "value": "United States"
      }
    ]
  },
  {
    "Type": [{
        "id": 5,
        "value": "Lead"
      },
      {
        "id": 6,
        "value": "Account"
      }
    ]
  }
]

Currently my CreateMap looks like this

CreateMap<DropdownValue, DropdownValueListDto>();

And my DropdownValueListDto like this

public class DropdownValueListDto
{
    public int Id { get; set; }
    public string Dropdown { get; set; }
    public string Value { get; set; }
}

My LINQ Operation looks like this:

    public async Task<IEnumerable<DropdownValue>> GetDropdownValues(string[] dropdowns)
    {
        var dropdownValues = _context.DropdownValues.OrderBy(x => x.Id).ThenBy(x => x.Dropdown).AsQueryable();

        if (dropdowns.Length != 0 || dropdowns != null)
        {
            dropdownValues = dropdownValues.Where(x => dropdowns.Contains(x.Dropdown));
        }

        var dropdownValuesToReturn = await dropdownValues.ToListAsync();

        return dropdownValuesToReturn;
    }

It would be great if someone could help me achieve this.

Thanks in advance

You don't want a simple map here, this is more of a transformation operation. - you could use linq to objects for this — GPW
– GPW, Commented Jul 10, 2018 at 16:15
I inserted my code for my LINQ operation above. How would I use the LINQ to objects with it? — A E
– A E, Commented Jul 10, 2018 at 16:21
Your JSON showing how you WANT the data to look doesn't match your DropDownValueListDto object... Is the JSON stuff more like you expect to see? — GPW
– GPW, Commented Jul 10, 2018 at 16:28
Yes the JSON stuff is more like I expect to see it. I tried to modify the DropdownValueListDto to match how I would like to see it, but that didn't work out. — A E
– A E, Commented Jul 10, 2018 at 16:30

GPW · Accepted Answer · 2018-07-11 08:45:18Z

1

based on your edits, I guess you'd have to do something like this:

//Your result class should actually look like this to match JSON:
class DropDownListDto
{
    public string Description {get;set;}
    //here you need an IEnumerable to store the list of Ids and values associated
    //with this drop-down.  you could create a class and declare a LIST<> of that
    //but I'll just use a dictionary instead.
    public Dictionary<int, string> DropDownValues{get;set;}
}

//Get source data
var source = await GetDropDownValues(<insert [] here>);

//transform list into IEnumerable<DropDownListDto>
var result = source
    //if we GROUP BY the Dropdown property then we'll get a distinct list of
    //of drop-downs.
    .GroupBy(x=>x.DropDown)
    //can then get the list of values and Ids from the resulting groups
    .Select(g=>new DropDownListDto
         {
              //key is the grouped by thing - drop down name..
              Description = g.Key,
              //doing a .select from the group result gives the elements
              //in that group only.  Get an anonymous type and cast that
              //to our required dictionary type
              DropDownValues = g
                .Select(x=>new{ key=x.Id, value = x.Value})
                .ToDictionary(k=>k.key, v=>v.value)
         });

That should give you something like what you want - I've not tested this though...

edited Jul 11, 2018 at 8:45

answered Jul 10, 2018 at 16:40

GPW

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1 Comment

GPW Over a year ago

@EE - no problem. I've realised this morning that I didn't do anything with the line declaring result as a new List<DropDownListDto> so I've removed that, and added a comment such that the result variable is actually going to be an IEnumerable<DropDownListDto>. You could cast this using .ToList() if you need an actual List<> type but it'll probably do what you want as-is.

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