using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public void Main()

    {

        SortedDictionary<CustomKey, string> dict = new SortedDictionary<CustomKey, string>(new KeyComparer());

        dict.Add(new CustomKey() { intKey = 1, sortingVariable = 17 }, "1");

        dict.Add(new CustomKey() { intKey = 2, sortingVariable = 6 }, "2");

        dict.Add(new CustomKey() { intKey = 5, sortingVariable = 12}, "expected value");

        dict.Add(new CustomKey() { intKey = 3, sortingVariable = 5 }, "3");

        dict.Add(new CustomKey() { intKey = 4, sortingVariable = 4 }, "4");

        string res;

        CustomKey comperativeKey = new CustomKey() { intKey = 5, sortingVariable = 17};

        dict.TryGetValue(comperativeKey , out res);

        Console.WriteLine(res);

        res = dict.Single(kvp => kvp.Key.Equals(comperativeKey)).Value;

        Console.WriteLine(res);

    }

}

​

public class KeyComparer : Comparer<CustomKey>

{

    public override int Compare(CustomKey x, CustomKey y)

    {

        return x.sortingVariable.CompareTo(y.sortingVariable);

    }

}

​

public struct CustomKey : IComparable

{

    public override bool Equals(object obj)

    {

        if (!(obj is CustomKey))

            return false;

        return ((CustomKey)obj).intKey == intKey && ((CustomKey)obj).objectKey == objectKey;

    }

​

    public override int GetHashCode()

    {

        return intKey.GetHashCode() ^ objectKey.GetHashCode();

    }

​

    public int CompareTo(object obj)

    {

        return sortingVariable.CompareTo(((CustomKey)obj).sortingVariable);

    }

​

    //Needs to participate in equality comparison for SortedDictionary.TryGetValue();

    public int intKey;

    public object objectKey;

    //Needs to be ignored in SortedDictionary.TryGetValue();

    public int sortingVariable;

    public string otherSortingVariable;

}