What is the fastest way to check if two sets are disjoint in C#?

See more:

.NET

LINQ

C#3.5

performance

I found a lot of answers online on how to check if two arrays are disjoint that involved the use of Enumerable.Intersect and Enumerable.Distinct calls, however I was wondering if there was a faster way to do what I need. I merely need to check if two arrays do not contain any common elements. I have three million arrays that I need to check with each other so I need to make a lot of calls and was wondering if there was any faster way to perform the following function:

private static bool checkIfDisjoint(int[] a, int[] b)
{
      for(int i = 0; i < a.Length; i++)
      {
            for (int j = 0; j < b.Length; j++)
            {
                   if (a[i] == b[j])
                         return false;
            }
      }
      return true;
}

I need to make a lot of calls and each of my arrays are less than length 4. So I was wondering if there was a faster way to achieve this.

What I have tried:

I've tried LINQ and the code block above, and was wondering if given the fact that the length of my arrays are never more than 4, and I have only 180 different characters which the arrays can contain, there was something I could do to make this operation faster.