using System;

using System.Collections.Generic;

using System.Xml;

using System.Linq;

using System.Data;

using System.Data.DataSetExtensions;

​

public class Program

{

    public static void Main()

    {

        PrintTable(ApplyLogicTo(GetData()));

    }

    private static void PrintTable(DataTable dt)

    {

        foreach(var dr in dt.AsEnumerable())

        {

            Console.Write(dr.Field<string>("Name"));

            Console.Write(": ");

            Console.Write(dr.Field<int>("Value"));

            Console.WriteLine();

        }

    }

    private static DataTable ApplyLogicTo(DataTable dt)

    {

        return dt.AsEnumerable()

            .GroupBy(row => row.Field<string>("Name"))

            .Select(grouping => grouping.MaxBy(row => row.Field<int>("Value")))

            .CopyToDataTable();

    }

    private static DataTable GetData()

    {

        var dt = new DataTable();

        dt.Columns.Add("Name", typeof(string));

        dt.Columns.Add("Value", typeof(int));

        dt.Rows.Add("Foo", 3);

        dt.Rows.Add("Bar", 5);

        dt.Rows.Add("Bar", 7);

        dt.Rows.Add("Baz", 1);

        return dt;

    }

}

​

public static class IEnumerableExtensions

{

    public static TSource MaxBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> selector) where TKey : IComparable<TKey>

    {

        if (source == null) throw new ArgumentNullException(nameof(source));

        if (selector == null) throw new ArgumentNullException(nameof(selector));

        var bestElement = default(TSource);

        var bestKey = default(TKey);

        bool hasValue = false;

        foreach(var element in source)

        {

            if (hasValue)

            {

                var key = selector(element);

                if (key.CompareTo(bestKey) > 0)

                {

                    bestKey = key;

                    bestElement = element;

                }

            }

            else

            {

                bestKey = selector(element);

                bestElement = element;

                hasValue = true;

            }

        }

        if (hasValue)

        {

            return bestElement;

        }

        else

        {

            throw new ArgumentException("Sequence contains no elements", nameof(source));

        }

    }

}