How to get list of items by common code in LINQ

Question

I have the following class in C#:

class AnalyteUnits {
  public string Analyte;
  public string Units;
}

So the data comes back looking like:

Analyte = "Ce", Units ="kg"
Analyte = "Fe", Units ="%"
Analyte = "Fe", Units = "g" etc etc

What I need is to shuffle this to look like:

analyte = "Fe", units = {"%", "g"}

How can I achieve this with LINQ?

Answer 1

You can try to GroupBy Analyte, e.g. given

AnalyteUnits[] data = new AnalyteUnits[] {
  new AnalyteUnits() { Analyte = "Ce", Units = "kg" },
  new AnalyteUnits() { Analyte = "Fe", Units = "%" },
  new AnalyteUnits() { Analyte = "Fe", Units = "g" },
};

You can put

var result = data
  .GroupBy(item => item.Analyte, item => item.Units)
  .ToDictionary(group => group.Key, group => group.ToArray());

// Let's have a look:
var report = string.Join(Environment.NewLine, result
  .Select(pair => $"{pair.Key} : {string.Join(", ", pair.Value)}"));

Console.Write(report);

Another possibility is Lookup instead of dictionary:

var lookup = data
  .GroupBy(item => item.Analyte, item => item.Units)
  .ToLookup(group => group.Key, group => group); 

// Let's have a look:
var report = string.Join(Environment.NewLine, lookup
  .Select(pair => $"{pair.Key} : {string.Join(", ", pair.Value)}"));

Console.Write(report); 

Fiddle