How to restructure an Object in C# using LINQ?

February 25, 2022

I have a data set as follows:

[
    {
        "Id": 1,
        "Country": "Uruguay",
        "Name": "Foo",
        "Status": "Completed",
    },
    {
        "Id": 2,
        "Country": "Uruguay",
        "Name": "Foo",
        "Status": "Completed",
    },
    {
        "Id": 3,
        "Country": "Germany",
        "Name": "Foo",
        "Status": "Completed",
    },
]

I want to transform and sort it by Country so that it looks as follows:

[
    {
        "Country": "Uruguay",
        "Details": [
         {
            "Id": 1,
            "Name": "Foo",
            "Status": "Completed",
         },
         {
            "Id": 2,
            "Name": "Foo",
            "Status": "Completed",
         },
        ],
    },
    {
        "Country": "Germany",
        "Details": [
         {
            "Id": 3,
            "Name": "Foo",
            "Status": "Completed",
         },
        ],
    },
],

These are the classes in C#:

public class Countries {
    public int Id { get; set; }
    public string Country { get; set; }
    public string Name { get; set; }
    public string Status { get; set; }
}

public class Details {
    public int Id { get; set; }
    public string Name { get; set; }
    public string Status { get; set; }
}

public class CountryList {
    public string Country { get; set; }
    public List<Details> Details { get; set; }
}

Some of what I have tried looks as followed:

var foo = countries
    .GroupBy(x => new Details { Id = x.Id, Name = x.Name, Status = x.Status })
    .Select( y => new CountryList 
     {
         // Country = y.Key. 
     }

var foo = countries
    .GroupBy(x => x.Country)
    .Select( y => new CountryList 
     {
         // Country = y.Key.
         Details = y.GroupBy(a => new Details 
         { 
            Id = a.Id, 
            Name = a.Name, 
            Status = a.Status  
         }).ToList() 
     }

I am having trouble working out how to use LINQ to solve this. I have done a handful of GroupBy operations in the past, but I wasn’t able to work this one out. How do I transform my dataset into the desired result?

>Solution :

You do not need second GroupBy

var foo = countries
    .GroupBy(x => x.Country)
    .Select(y => new CountryList 
     {
         Country = y.Key,
         Details = y.Select(a => new Details 
         { 
            Id = a.Id, 
            Name = a.Name, 
            Status = a.Status  
         }).ToList() 
     };