CODEWITHSUNDEEP
c#
osueboy
osueboy

Reputation: 143

C# IComparable IComparer with additional Param

How can I implement IComparer

int CompareTo(object obj)

with an additional parameter, like

int CompareTo(object obj, Dictionary<int, int> preferences)

preferences is a dictionary with Id and NumberOfClicks<int, int>

What I want is compare contents which have categoryId by the number of clicks in the dictionary,

Example Cat 1 has 3 clicks, Cat 2 has 6 clicks.

Sort by comparing preferences[this.CategoryId].value > preferences[object.CategoryId].value

So they are sorted by category, but in relation to the Dictionary.

Upvotes: 3

Views: 843

Answers (2)

Servy
Servy

Reputation: 203820

Create a separate comparer class that implements IComparer<T>, rather than having the type itself implement IComparable, and have it accept the Dictionary in its constructor. That comparer can then use the dictionary when it compares instances of your object.

Upvotes: 0

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726569

You cannot pass extra arguments to IComparer's Compare method, because method signature must match the signature in the interface.

What you can do is to construct an instance of IComparer with the extra parameter, store it in the instance, and use inside CompareTo as needed:

class MyComparer : IComparer<object> {
    private readonly IDictionary<int, int> preferences;
    public MyComparer(IDictionary<int, int> preferences) {
        this.preferences = preferences;
    }
    public int Compare(object a, object b) {
        ... // Perform the comparison with preferences in scope
    }
}

Upvotes: 5

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