Question

I am able to return a grouped list of items from my collection using the following code:

var items = collection.SelectMany(myObj => myObj.ToNames)
    .GroupBy(name => name)
    .Select(g => new { Name = g.Key, Count = g.Count() });

The above code gives me a nice list of unique names and the number of times they were found in the collection. I now have a need to do the same thing, but group the Names from two seperate collections found in the same MyObj. I now want to group myObj.ToNames and myObj.FromNames in the same manner – along with getting the overall unique count for each unique name found (no matter which collection it was found in).

Is this possible?

Answer 1

Union:

var items = collection.SelectMany(myObj => myObj.ToNames.Union(myObj.FromNames))
    .GroupBy(name => name)
    .Select(g => new { Name = g.Key, Count = g.Count() });

Concat:

var items = collection.SelectMany(myObj => myObj.ToNames.Concat(myObj.FromNames))
    .GroupBy(name => name)
    .Select(g => new { Name = g.Key, Count = g.Count() });