Question

I have an array of arrays – information about selection in Excel using VSTO, where each element means start and end selection position.

For example,

int[][] selection = { new int[] { 1 }, // column A new int[] { 6 }, // column F new int[] { 6 }, // column F new int[] { 8, 9 } // columns H:I new int[] { 8, 9 } // columns H:I new int[] { 12, 15 } // columns L:O }; 

Could you please help me to find a way, maybe using LINQ or Extension methods, to remove duplicated elements? I mean: F and F, H:I and H:I, etc.

Answer 1

If you want to use a pure LINQ/extension method solution, then you’ll need to define your own implementation of IEqualityComparer for arrays/sequences. (Unless I’m missing something obvious, there’s no pre-existing array or sequence comparer in the BCL). This isn’t terribly hard however – here’s an example of one that should do the job pretty well:

public class SequenceEqualityComparer<T> : IEqualityComparer<IEnumerable<T>> {     public bool Equals(IEnumerable<T> x, IEnumerable<T> y)     {         return Enumerable.SequenceEqual(x, y);     }      // Probably not the best hash function for an ordered list, but it should do the job in most cases.     public int GetHashCode(IEnumerable<T> obj)     {         int hash = 0;         int i = 0;         foreach (var element in obj)             hash = unchecked((hash * 37 + hash) + (element.GetHashCode() << (i++ % 16)));         return hash;     } } 

The advantage of this is that you can then simply call the following to remove any duplicate arrays.

var result = selection.Distinct(new SequenceEqualityComparer<int>()).ToArray(); 

Hope that helps.