LINQ GroupBy and select a list of other property values

I have pairs as such:

public class AnalyteUnitPair
	{
		public string Analyte { get; set; }
		public string Unit { get; set; }
	}

and I need to turn the list of these into a reshuffled grouped by as such:

what I have

Analyte ="Ce", Unit="g"
Analyte ="Ce", Unit="%"
Analyte ="Ce", Unit="ppm"
Analyte ="Dy", Unit="kg"
Analyte ="Dy", Unit="%"
Analyte ="Dy", Unit="ppm"

what I need is to convert the list above into the list of objects

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

	}

that would look like this

Analyte="Ce", Units="g:g,%:%,ppm:ppm";
Analyte="Dy", Units="kg:kg,%:%,ppm:ppm";

Please do not suggest Dictionary, I don't want to deal with them on the JS side.

How's this:

var listOfPairs = new List<AnalyteUnitPair>
{
    new AnalyteUnitPair { Analyte = "Ce",Unit = "g" },
    new AnalyteUnitPair { Analyte = "Ce",Unit = "%"},
    new AnalyteUnitPair { Analyte = "Ce",Unit = "ppm"},
    new AnalyteUnitPair { Analyte = "Dy",Unit = "kg"},
    new AnalyteUnitPair { Analyte = "Dy",Unit = "%"},
    new AnalyteUnitPair { Analyte = "Dy",Unit = "ppm"}
};

var analyteUnitsQuery =
    from pair in listOfPairs
    group pair by pair.Analyte into g
    select new AnalyteUnits
    {
        Analyte = g.Key,
        Units = string.Join(',', g.Select(pair => $"{pair.Unit}:{pair.Unit}"))
    };

foreach (var analyteUnits in analyteUnitsQuery)
{
    Console.WriteLine($"Analyte={analyteUnits.Analyte}, Units={analyteUnits.Units}");
}

public class AnalyteUnitPair
{
    public string Analyte { get; set; }
    public string Unit { get; set; }
}

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

First group by the Analyte, then you can select all the Units for each group.

var condensed = originalList
    .GroupBy(item => item.Analyte)
    .Select(group => new AnalyteUnitPair()
    {
        Analyte = group.Key,
        Unit = string.Join(",", group.Select(item => $"{item.Unit}:{item.Unit}"))
    });