Question

I have 3 collection list as below.

public static List<Thing> English = new List<Thing>
{
    new Thing {ID = 1, Stuff = "one"},
    new Thing {ID = 2, Stuff = "two"},
    new Thing {ID = 3, Stuff = "three"}
};

public static List<Thing> Spanish = new List<Thing>
{
    new Thing {ID = 1, Stuff = "uno"},
    new Thing {ID = 2, Stuff = "dos"},
    new Thing {ID = 3, Stuff = "tres"},
    new Thing {ID = 4, Stuff = "cuatro"}
};

public static List<Thing> German = new List<Thing>
{
    new Thing {ID = 1, Stuff = "eins"},
    new Thing {ID = 2, Stuff = "zwei"},
    new Thing {ID = 3, Stuff = "drei"}
};

During runtime, the length of the list may vary. For eg, German may take 5 values, english with 2 and spanish with one.

I need to find which list has the max value and need to get the output in the below format.

      Id English  German  Spanish
       1  one      eins    uno
       2  two      zwei    dos
       3  three    drei    tres
       4                   cuatro

Can you please help me to solve this.

Answer 1

Try this:

English.Select(t => new Tuple<Thing,int>(t, 1)).Concatenate(
    German.Select(t => new Tuple<Thing,int>(t, 2)).Concatenate(
        Spanish.Select(t => new Tuple<Thing,int>(t, 3))
    )
).GroupBy(p => p.Item1.ID)
.Select(g => new {
    Id = g.Key
,   English = g.Where(t => t.Item2==1).Select(t => t.Item2.Stuff).SingleOrDefault()
,   German = g.Where(t => t.Item2==2).Select(t => t.Item2.Stuff).SingleOrDefault()
,   Spanish = g.Where(t => t.Item2==3).Select(t => t.Item2.Stuff).SingleOrDefault()
});

The idea is to tag the original items with their collection origin (1 for English, 2 for German, 3 for Spanish), group them by ID, and then pull the details for individual languages using the tag that we added in the first step.