c# Sorting an array with IComparable Interface

Question

I have a jobArray array with 5 jobs that contain a description, hours needed to complete, and an hourly pay that a user enters.

I need to sort the array when it prints by ascending order of the total fee (hours * hourly pay).

The assignment requires I use the IComparable interface when doing so but I'm unsure how to use it. Any help would be appreciated, thank you

Here is my job class

class Job : IComparable
{

    public Job(string description, int hours, double hourRate, double fee)
    {
        Description = description;
        hoursToComplete = hoursToComplete;
        hourlyRate = hourlyRate;
        totalFee = totalFee;

    }

This is the interface I've done to compare totalFees

    public int CompareTo(Job o)
    {
        int returnVal;
        Job temp = (Job)o;
        if (this.totalFee > temp.totalFee)
            returnVal = 1;
        else
            if (this.totalFee < temp.totalFee)
                returnVal = -1;
            else
                returnVal = 0;
        return returnVal;

    }

I'm unsure what do to from here as to sorting the jobs when they print out by total fees.

I think you did it correct. Now just add the objects of this class to a list and use sort() method. — Rishabh Kumar
– Rishabh Kumar, Commented Oct 3, 2016 at 5:05
Your code will not compile. There are a number of obvious errors in your code that has nothing to do with IComparable or sorting. You should first attempt to fix it before trying to do anything more complex. — Vijay
– Vijay, Commented Oct 3, 2016 at 5:07

Pavan Chandaka · Accepted Answer · 2016-10-03 05:10:33Z

3

When you override "compareTo" method, and if you call "sort", the overrideen method is automatically called.

Here is a good example from microsoft for arrays. https://support.microsoft.com/en-us/kb/320727

Below is a an example (pseudo code) of "LIST"

List<Job> list = new List<Job>();

list.Add(new Job() { //Intialize arguments });
list.Add(new Job() { //Intialize arguments });
list.Add(new Job() { //Intialize arguments });
list.Add(new Job() { //Intialize arguments });
list.Add(new Job() { //Intialize arguments });

// Uses IComparable.CompareTo()
list.Sort();

answered Oct 3, 2016 at 5:10

Pavan Chandaka

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Comments

Mrinal Kamboj · Accepted Answer · 2016-10-03 05:26:01Z

2

Here's the working version of your code:

class Job : IComparable<Job>
{
    public string Description { get; set;}

    public int HoursToComplete { get; set;}

    public double HourlyRate { get; set;}

    public double TotalFee { get; set;}

    public Job(string description, 
               int hoursToComplete, 
               double hourlyRate, 
               double totalFee)
    {
        Description = description;
        HoursToComplete = hoursToComplete;
        HourlyRate = hourlyRate;
        TotalFee = totalFee;
    }

    public int CompareTo(Job otherJob)
    {
        int returnVal;

        if (this.TotalFee > otherJob.TotalFee)
            returnVal = 1;
        else
            if (this.TotalFee < otherJob.TotalFee)
            returnVal = -1;
        else
            returnVal = 0;

        return returnVal;
    }
}

Now since you have implemented IComparable<Job>, then on the given List<Job>, just call Sort, which will automatically call Job class CompareTo, instead of object class. Also note I have used the generic version IComparable<Job>, instead of IComparable, to avoid unncessary type-casting

answered Oct 3, 2016 at 5:26

Mrinal Kamboj

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4 Comments

John Over a year ago

thank you. would i call it when i print out the array? when i try to call .sort it does not appear on the intellisense.

Mrinal Kamboj Over a year ago

Call ArrayObject.ToList(), then call Sort on the List

Vijay Over a year ago

You can simplify CompareTo to a one-liner. return this.TotalFee - otherJob.TotalFee

Mrinal Kamboj Over a year ago

In this case true, but will not work as expected in all the cases, where multiple fields are involved, therefore used the standard comparison notation, modifying the OP code. Nonetheless thanks

JPil · Accepted Answer · 2016-10-03 05:21:39Z

2

Try CompareTo function as given below:

public int CompareTo(object obj)
{
     job tempList = (job)obj;
     return tempList.totalFee.CompareTo(totalFee);
}

Then call your method.

list.Sort()

answered Oct 3, 2016 at 5:21

JPil

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