Checking equality for two byte arrays

Question

I am checking the equality of two byte arrays, and I wanted some help because what I have returns false even though the arrays should be equal.

Within my debug I could see both of a1 and b1 are equal, but it is not going inside the while loop to increment i.

public bool Equality(byte[] a1, byte[] b1) {     int i;     bool bEqual;     if (a1.Length == b1.Length)     {         i = 0;         while ((i < a1.Length) && (a1[i]==b1[i]))         {             i++;         }          if (i == a1.Length)         {             bEqual = true;         }     }     return bEqual; } 

This always returns false: (a1[i]==b1[i]).

Answer 1

You need to add a return value somewhere. This should work:

public bool Equality(byte[] a1, byte[] b1) {    int i;    if (a1.Length == b1.Length)    {       i = 0;       while (i < a1.Length && (a1[i]==b1[i])) //Earlier it was a1[i]!=b1[i]       {           i++;       }       if (i == a1.Length)       {           return true;       }    }     return false; } 

But this is much simpler:

return a1.SequenceEqual(b1); 

Alternatively, you could use IStructuralEquatable from .NET 4:

return ((IStructuralEquatable)a1).Equals(b1, StructuralComparisons.StructuralEqualityComparer) 

---

If performance is a concern, I'd recommend rewriting your code to use the Binary class, which is specifically optimized for this kind of use case:

public bool Equality(Binary a1, Binary b1) {     return a1.Equals(b1); } 

A quick benchmark on my machine gives the following stats:

Method                   Min         Max         Avg binary equal:          0.868       3.076       0.933    (best) for loop:              2.636      10.004       3.065 sequence equal:        8.940      30.124      10.258 structure equal:     155.644     381.052     170.693 

Download this LINQPad file to run the benchmark yourself.