Question

I was doing homework in C# that required sorting an array. I could sort an array of integers using

Array.sort<int>(a, delegate(int x, int y) { return y-x;});

However if i want to do it from certain position and certain length

Array.sort<int>(a, 0, m, delegate(int x, int y) { return y-x;});

I get compilation error: “Cannot convert anonymous method to type ‘System.Collections.Generic.IComparer’ because it is not a delegate type”.
I have solved the problem just by using

Array.sort<int>(a, 0, m);

and doing all other stuff backwards. Why it was giving me an error, and how can change it to work?

Thanks for help

Answer 1

The method the first example is calling has the signature:

Array.Sort(int[] array, Comparison<int> comparison) 

The delegate you are using is for the Comparison. There is not an overload of Array.Sort that has a index, length and Comparison.

The method you are trying to call has the following signature:

Array.Sort(int[] array, int index, int length, IComparer<int> comparer) 

Note IComparer, not Comparison

If you need custom sorting. You will need to create a class that implements IComparer as this is what the 4th parameter is expecting.

Alternatively, try the .OrderByDescending extension method which is available when you include using System.Linq;