Reverse Sorting with IComparable

Question

I have code like this -

List<User> users;
protected class User : IComparable<User>
{
    public string name;
    public string email;
    public decimal total;
    public string address;
    public string company;
    public string origin;
    public int CompareTo(User b)
    {
        return this.total.CompareTo(b.total);

    }
}

For a table that is sorted by the number of points a user has. It sorts in ascending order, but need to change it to descending order. It uses users.Sort(), but I can't seem to figure out how to make it sort in reverse order.

score 16 · Accepted Answer · answered Jul 31 '14 at 16:02

16

If you want to reverse the order, just reverse the comparison:

public int CompareTo(User b)
{
    return b.total.CompareTo(this.total);
}

answered Jul 31 '14 at 16:02

Selman Genç

100,147
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score 6 · Answer 2 · answered Jul 31 '14 at 16:02

6

If your User class can be changed to sort in reverse order, you can try other answers which suggests modifying CompareTo method. Otherwise try the following.

users.Sort();//Sort normally
users.Sort((x, y) => y.CompareTo(x));//Reverse sort

answered Jul 31 '14 at 16:02

Sriram Sakthivel

72,067
7
111
189

score 3 · Answer 3 · answered Jul 31 '14 at 16:02

3

Just reverse the parameters in your comparison. So instead of:

return this.total.CompareTo(b.total);

Just do:

return b.total.CompareTo(this.total);

answered Jul 31 '14 at 16:02

DavidG

113,891
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score 1 · Answer 4 · answered Jul 19 '19 at 01:32

1

public int CompareTo(User b)
{
    return this.total.CompareTo(b.total) * -1;

}

answered Jul 19 '19 at 01:32

TimChang

2,249
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1

Edge case problem here! CompareTo doesn't limit range of return values, and due to 2s complement numbers and overflow we have the situation where (Int32.MinValue * -1 == int32.MinValue) which could cause a problem. – Paul Westcott Oct 25 '19 at 21:36

Reverse Sorting with IComparable

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