Shortest distance between two arrays

Given two sorted array in non-descending order, each contains positive integers
The distance is define as following
pick up a number from each array, compute their difference
return the shortest distance among them-that's the distance between the two arrays
example
int[] a = {1, 3, 5, 7 , 9} ;
int[] b = {2, 4, 8} ;
The result is 1

 1 public int Distance(int[] a, int[] b)
 2 {
 3     int d = int.MaxValue;
 4     int i = 0;
 5     int j = 0;
 6     while (i < a.Length && j < b.Length)
 7     {
 8         if (a[i] < b[j])
 9         {
10             d = Math.Min(d, Math.Abs(a[i] - b[j]));
11             i++;
12         }
13         else if (a[i] == b[j])// note, 0 is the shortest distance of all
14             return 0; // if we got 0, no need to test the subsequent values, return immediately
15         else
16         {
17             d = Math.Min(d, Math.Abs(a[i] - b[j]));
18             j++;
19         }
20     }
21     return d;
22 }