How to write linq query with list of two joined tables a and B, then grouped by id of a, and with amount of joined rows from B

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How to write Linq query with list of two joined tables A and B, then grouped by id of A, and with amount of joined rows from B

For example

class A{
int Id,
int BId,
string AName
};

class B{
int Id,
string description
};

And to display as follows (after joins of A with B) A.Bid = B.Id

A Id | count(Id) | AName

What I have tried:

How to write Linq query with list of two joined tables A and B, then grouped by id of A, and with amount of joined rows from B

For example

class A{
   int Id,
   int BId,
   string AName
};

class B{
   int Id,
   string description
};

And to display as follows (after joins of A with B) A.Bid = B.Id

A Id |  count(Id) | AName

Posted 29-May-18 3:29am

Piterek

Updated 13-Jun-18 5:05am

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Clifford Nelson · Accepted Answer · 2018-06-13T05:06:00

Think this is what you are looking for:

  class Program
    {
        static void Main(string[] args)
        {
            var listA = new List<A>
            {
                new A{Id = 1, BId = 1, AName = "A" },
                new A{Id = 2, BId = 2, AName = "B" },
            };
            var listB = new List
            {
                new B{Id = 1,  description = "dA" },
                new B{Id = 2, description = "dB" },
            };

            var result = listA.Select(a => 
new { Id = a.Id, Name = a.AName, count = listB.Count(b => b.Id == a.Id) });
        }

        class A
        {
          public  int Id { get; set; }
            public int BId { get; set; }
            public string AName { get; set; }
        };

        class B
        {
            public int Id { get; set; }
            public string description { get; set; }
        };
    }