using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

public class MyModel

{

    public int ElementID { get; set; }

    public string ElementName { get; set; }

    public string ElementValue { get; set; }

}

    public static void Main()

    {

var list = new List<MyModel>();

​

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name1", ElementValue = "Id1Name1Value1"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name1", ElementValue = "Id1Name1Value2"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name2", ElementValue = "Id1Name2Value1"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name3", ElementValue = "Id1Name3Value1"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name3", ElementValue = "Id1Name3Value2"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name4", ElementValue = "Id1Name4Value1"});

        list.Add(new MyModel {ElementID = 1, ElementName = "Id1Name4", ElementValue = "Id1Name4Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name1", ElementValue = "Id2Name1Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name1", ElementValue = "Id2Name1Value2"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name2", ElementValue = "Id2Name2Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name3", ElementValue = "Id2Name3Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name3", ElementValue = "Id2Name3Value2"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name4", ElementValue = "Id2Name4Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name5", ElementValue = "Id2Name5Value1"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name5", ElementValue = "Id2Name5Value2"});

        list.Add(new MyModel {ElementID = 2, ElementName = "Id2Name5", ElementValue = "Id2Name5Value3"});

        var selectedGroups = list.GroupBy(i => 

            new

            {

                i.ElementID,

                i.ElementName

            }).

            Where(g => g.Select(i => i.ElementValue).Distinct().Count() > 1);

        foreach (var group in selectedGroups)

        {

            Console.WriteLine($"{group.Key.ElementID} {group.Key.ElementName}");

        }

    }

}