Merge a list of object array c#

Question

I have list of object array (List<object[]> a) that come from different sources (files, sql, webservices) and I need a way to join them. For example, I have this two list:

        List<object[]> listA = new List<object[]>();
        object[] a = new object[] { 1, "A", 1200, "2016-12-31" };
        listA.Add(a);
        a = new object[] { 2, "B", 5200, "2016-12-31" };
        listA.Add(a);
        a = new object[] { 3, "C", 3500, "2016-12-31" };
        listA.Add(a);
        a = new object[] { 4, "D", 100, "2016-12-31" };
        listA.Add(a);

        List<object[]> listB = new List<object[]>();
        object[] b = new object[] { 44,  859, "2016-12-08" };
        listB.Add(b);
        b = new object[] { 23, 851, "2016-12-07" };
        listB.Add(b);
        b = new object[] { 31, 785, "2016-12-09" };
        listB.Add(b);

And the result will be this one:

        List<object[]> listC = new List<object[]>();
        object[] c = new object[] { 1, "A", 1200+859, 44, "2016-12-08" };
        listC.Add(c);
        c = new object[] { 2, "B", 5200+851, 23,  "2016-12-07" };
        listC.Add(c);
        c = new object[] { 3, "C", 3500+785, 31, "2016-12-09" };
        listC.Add(c);
        c = new object[] { 4, "D", 100, null, null };
        listC.Add(c);

The lists are bigger than in the example and I have to configure how to merge then but if I found a way to do this in linq is the half of the way. Any ideas?

Answer 1

You can zip both sequences and concat with left items from listA:

listA.Zip(listB, (a, b) => 
         new object[] { a[0], a[1], (int)a[2] + (int)b[1], b[0], b[2] })
     .Concat(listA.Skip(listB.Count).Select(a => 
         new object[] { a[0], a[1], a[2], null, null }))

You can also use group join or select items from second list by index of item in first list.

---

I also suggest you to use custom classes instead of arrays of objects to make your code more readable, get nice type checking, descriptive properties, and intellisense. E.g.

public class Foo
{
   public int Id { get; set; }
   public string Name { get; set; }
   public int Value { get; set; }
   public DateTime Date { get; set; }
}

And

public class Bar
{
   public int Id { get; set; }
   public int Value { get; set; }
   public DateTime Date { get; set; }
}

Of course you should use more appropriate names here. Now your code will look like

List<Foo> foos = new List<Foo> {
   new Foo { Id=1, Name="A", Value=1200, Date=new DateTime(2016,12,31) },
   new Foo { Id=2, Name="B", Value=5200, Date=new DateTime(2016,12,31) },
   new Foo { Id=3, Name="C", Value=3500, Date=new DateTime(2016,12,31) },
   new Foo { Id=4, Name="D", Value=100, Date=new DateTime(2016,12,31) },
};

List<Bar> bars = new List<Bar> {
   new Bar { Id=44, Value=859, Date=new DateTime(2016,12,8) },
   new Bar { Id=23, Value=851, Date=new DateTime(2016,12,7) },
   new Bar { Id=31, Value=785, Date=new DateTime(2016,12,9) }
};

You can also create custom type to hold combined data.

public class Result
{
    public int FooId {get; set; }
    public string Name {get; set; }
    public int Value {get;set;}
    public int? BarId {get;set;}
    public DateTime? Date {get; set;}
}

And getting results will look like

var results = foos.Zip(bars, (f, b) => new Result{ 
    FooId = f.Id, Name = f.Name, Value = f.Value + b.Value, BarId =  b.Id, Date = b.Date
}).Concat(foos.Skip(bars.Count).Select(f => new Result {
    FooId = f.Id, Name = f.Name, Value = f.Value
}));

Try Working Code