Linq how to union array of objects inside list and group by value

Question

I've got a problem and need some help. I've got a list of objects which have many properties, but only two are important "From" and "To".

objectData { "From" : "ContactDTO", "To" : ["ContactDTO"], ...//other fields }

contactDto { "email" : "string", ... other fields }

and I need to return new list with unique entries "From", array of contacts "To" without duplicates.

Test Data:

{ 
   "From": { "email" : "[email protected]"}, 
   "To": "[{ "email" : "[email protected]"}, { "email" : "[email protected]"}]"
},
{ 
   "From": { "email" : "[email protected]"}, 
   "To": "[{ "email" : "[email protected]"}, { "email" : "[email protected]"}]"
},
{ 
   "From": { "email" : "[email protected]"}, 
   "To": "[{ "email" : "[email protected]"}, { "email" : "[email protected]"}]"
},

Should Return:

[
"From": { "email" : "[email protected]"}, 
   "To": "[{ "email" : "[email protected]"}, { "email" : "[email protected]"}, { "email" : "[email protected]"}]"
{ 
   "From": { "email" : "[email protected]"}, 
   "To": "[{ "email" : "[email protected]"}, { "email" : "[email protected]"}]"
}
]

I know how to do it in a loop, but I would like to make it more readable and clean with using linq.

I've tried:

var newData = data.Where(x => IsReview(x))
                .Select(x => 
                new { 
                    From = x.From.EmailAddress, 
                    List = x.To.Select(z => z.EmailAddress).ToList() 
                }).GroupBy(y => y.From);

What issue you faced in your attempt? Do you want unique email addresses in List? — Prasad Telkikar
– Prasad Telkikar, Commented Jun 20, 2020 at 17:25
Well u r almost there, try adding select to groupby. Inside select apply selectmany to flatten the emails followed by distinct — neelesh bodgal
– neelesh bodgal, Commented Jun 20, 2020 at 17:34

Mohammed Sajid · Accepted Answer · 2020-06-20 19:28:12Z

2

You could Select new object after GroupBy and use SelectMany to flatten emails in one list, like the following code:

var newData = data.Where(x => IsReview(x))
    .Select(x => new 
    { 
        From = x.From.EmailAddress, 
        List = x.To.Select(z => z.EmailAddress).ToList() 
    }).GroupBy(y => y.From)
    .Select(x => new
    {
        From = x.Key,
        To = x.SelectMany(y => y.List).ToList()
    });

I hope you find this helpful.

edited Jun 20, 2020 at 19:28

answered Jun 20, 2020 at 17:26

Mohammed Sajid

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2 Comments

user2470967 Over a year ago

thank you for your help, I've modified it a bit, but manage to get it working. I'm marking your answer as correct one, have a great day.

Mohammed Sajid Over a year ago

you're welcome, was glad to help, have a good day too.

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