using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Foo[] data = {

             new Foo() {Weight = 1.2, Name = "1", Tdesc = 0.0},

            new Foo() {Weight = 4.0, Name = "2", Tdesc=3.1},

            new Foo() {Weight = 1.2, Name = "3", Tdesc = 1.1},

            new Foo() {Weight = 4.0, Name = "4", Tdesc = 2.6}

        };

        var results = Test(data);

        foreach(var result in results) {Console.WriteLine(result);}

    }

    public static IEnumerable<Foo> Test(IEnumerable<Foo> data)

    {

        return data.GroupBy(i => i.Weight, i=>i).

            Select(g => g.OrderBy(i=>-1*i.Tdesc).First());

    }

​

//Dim MaxPerWeight = weightGroups.Select(Function(g) g.Max(Function(i) i.Tdesc))

}

​

public class Foo

{

    public double Weight{get;set;}

    public string Name{get;set;}

    public double Tdesc{get;set;}

    public override string ToString()

    {

        return $"Name: {Name}; Weight: {Weight}; Tdesc: {Tdesc}";

    }

}