Sorting Genric List By Their Properties

This tip demonstrates how to sort generic lists in a much simpler way without writing much complex loops and comparison logic.

The following steps are required for sorting the list:

1. Create class for sorting and implement interface IComparable<Type> wheres Type will reflect class for comparison

Ex: public class Racer : IComparable<Racer>

2. Add properties in the above class

Ex:

public string FirstName { get; set; }

public string LastName { get; set; }

public string Country { get; set; }

public int Wins { get; set; }

3. You have to override method of IComparable but it won't be executed for sorting

Ex:

public int CompareTo(Racer other)

4. Create a class for doing comparison which will implement IComparer for doing comparison

Ex:

public class RacerComparer : IComparer<Racer>

5. Add enum to save what will be items through sorting will be done.

Ex:

public enum CompareType

6. Override compare function of IComparer

Ex:

public int Compare(Racer x, Racer y)

You are done.

The complete code:

class Program

{

static void Main(string[] args)

{

//Create list of Racers

List<Racer> racers = new List<Racer>();

racers.Add(new Racer() { FirstName = "Vikash", LastName = "Kumar", Country = "India", Wins = 40 });

racers.Add(new Racer() { FirstName = "Graham", LastName = "Hill", Country = "UK", Wins = 14 });

racers.Add(new Racer() { FirstName = "Emerson", LastName = "Fittipaldi", Country = "Brazil", Wins = 14 });

racers.Add(new Racer() { FirstName = "Mario", LastName = "Andretti", Country = "USA", Wins = 12 });

racers.Add(new Racer() { FirstName = "Michael", LastName = "Schumacher", Country = "Germany", Wins = 91 });

racers.Add(new Racer() { FirstName = "Mika", LastName = "Hakkinen", Country = "Finland", Wins = 20 });

racers.Add(new Racer() { FirstName = "Alain", LastName = "Prost", Country = "France", Wins = 51 });

racers.Add(new Racer() { FirstName = "Niki", LastName = "Lauda", Country = "Austria", Wins = 25 });

//Sort racer by passing RacerComparer instance with type of sorting that is required

racers.Sort(new RacerComparer(RacerComparer.CompareType.Wins));

//Display result on Console

racers.ForEach(Console.WriteLine);

}

/// <summary>

/// Class for storing Racer specific details and behaviour

/// </summary>

public class Racer : IComparable<Racer>

{

//properties for class

public string FirstName { get; set; }

public string LastName { get; set; }

public string Country { get; set; }

public int Wins { get; set; }

/// <summary>

/// Overrided method of ToString()

/// </summary>

/// <returns>Racer's First name and Last Name</returns>

public override string ToString()

{

return FirstName + " " + LastName;

}

/// <summary>

/// Overrided method of IComparable()

/// Compares with current instance on their name

/// </summary>

/// <param name="other">Racer object</param>

/// <returns>returns integer whether comparison is successuful or not</returns>

public int CompareTo(Racer other)

{

int compare = this.LastName.CompareTo(other.LastName);

if (compare == 0)

return this.FirstName.CompareTo(other.FirstName);

return compare;

}

/// <summary>

/// Racer compare class

/// </summary>

public class RacerComparer : IComparer<Racer>

{

//Type of comparison needed

public enum CompareType

{

FirstName,

LastName,

Country,

Wins

}

private CompareType compareType;

/// <summary>

/// Cunstructor for intializing RacerComparer with CompareType

/// </summary>

/// <param name="compareType">Type of comparison</param>

public RacerComparer(CompareType compareType)

{

this.compareType = compareType;

}

/// <summary>

/// Comaparison between two objects

/// sorting will be done by this method

/// </summary>

/// <param name="x">First racer object</param>

/// <param name="y">Second racer object</param>

/// <returns>returns integer whether comparison is successuful or not</returns>

public int Compare(Racer x, Racer y)

{

if (x == null) throw new ArgumentNullException("x");

if (y == null) throw new ArgumentNullException("y");

int result;

//do comparison basis on CompareType and return result

switch (compareType)

{

case CompareType.FirstName:

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

case CompareType.LastName:

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

case CompareType.Country:

if ((result = x.Country.CompareTo(y.Country)) == 0)

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

else

return result;

case CompareType.Wins:

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

default:

throw new ArgumentException("Invalid Compare Type");