Linq query to return object list with multiple child arrays

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    var list = new List<Franchise>()
    {
     new Franchise()
     {Id = 10, Name = "Franchise1", Code= "DD1", IsDomestic= 1, ParentCompanyId=1, GroupId=100 },        
     new Franchise()
     {Id = 10, Name = "Franchise1", Code= "DD1", IsDomestic= 1, ParentCompanyId=2, GroupId=100 },
     new Franchise()
     {Id = 10, Name = "Franchise1", Code= "DD1", IsDomestic= 1, ParentCompanyId=3, GroupId=200 },
     new Franchise()
     {Id = 15, Name = "Franchise5", Code= "FD1", IsDomestic= 0, ParentCompanyId=4, GroupId=300 },
     new Franchise()
     {Id = 15, Name = "Franchise5", Code= "FD1", IsDomestic= 0, ParentCompanyId=3, GroupId=300 },
     new Franchise()
     {Id = 15, Name = "Franchise5", Code= "FD1", IsDomestic= 0, ParentCompanyId=2, GroupId=400 },
   };

I want this to be transformed to list of the class below using LINQ

    public class FranchiseNew
    {
        public int Id { get; set; }
        public string Name{ get; set; }
        public int[] CategoryIds { get; set; }
        public int[] DivisionIds { get; set; }
        public int IsDomestic{ get; set; }
     }

output - one row per franchise with ParentCompanyIds and GroupIds in arrays

    var list = new List<Franchise>()
    {
       new Franchise()
       {Id = 10, Name = "Franchise1", Code= "DD1", IsDomestic= 1, ParentCompanyIds=[1, 2, 3], GroupIds = [100, 200 ]},        
       new Franchise()
       {Id = 15, Name = "Franchise2", Code= "FD1", IsDomestic= 0, ParentCompanyIds=[4, 3, 2], GroupIds = [300, 400] }
    };

What is the efficient LINQ query to achieve this? Thanks in advance.

sri harsha · Accepted Answer · 2020-06-06 05:30:29Z

1

You can try like below:

var collectionGroup = list.GroupBy(x => new { x.Name, x.Id, x.Code, x.IsDomestic }).ToList();
var result = collectionGroup.Select(x => new FranchiseNew
        {
            Id = x.Key.Id,
            Name = x.Key.Name,
            Code = x.Key.Code,
            IsDomestic = x.Key.IsDomestic,
            CategoryIds = x.GroupBy(s => s.ParentCompanyId).Select(y => y.Key).ToArray(),
            DivisionIds = x.GroupBy(s => s.GroupId).Select(y => y.Key).ToArray()
        }).ToList();

And in you're FranchiseNew model, add Code field.

answered Jun 6, 2020 at 5:30

sri harsha

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3 Comments

Guru Stron Over a year ago

You don't need to materialize collectionGroup via .ToList. Using GroupBy to select distinct ids is overkill, use .Select(s => s.GroupId).Distinct()

techie net20 Over a year ago

Thanks sri harsha and Guru Stron. The above solution works. But in my problem, when I have the type Franchise. I do not have the Franchise class and the data comes from a data table. When I try to use the same on the x.GroupBy(s => s.GroupId), I get the error 'Represents an object whose operations will be resolved at runtime'.

techie net20 Over a year ago

Thanks Sri harsha nad Guru Stron. This solution works.

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