Question: I have HahSet collection of int[9] arrays and want know if HashSe already contains that array.
for example

```
       HashSet<int[]> set = new HashSet<int[]>();
       int[] a=new int[9]{1,2,3,4,5,6,7,8,9};
       set.Add(a);
       int[] a2=new int[9]{1,2,3,4,5,6,7,8,9};
       if(!set.Contains(a2))
          set.Add(a2);

```

How can I override or implement own Equals method so that HastSet.Contains would behave like Arrays.SequenceEquals?

Answer: 
You need to provide an implementation of `IEqualityComparer<int[]>`, and use the constructor that takes your custom comparer:

```
class MyEqCmpForInt : IEqualityComparer<int[]> {
    public bool Equals(int[] a, int[] b) {
        ...
    }
    public int GetHashCode(int[] data) {
        ...
    }
}

HashSet<int[]> set = new HashSet<int[]>(new MyEqCmpForInt());

```
The hash set class has [a constructor that takes an equality comparer](http://msdn.microsoft.com/en-us/library/bb359100.aspx). Use it.