Merge Arrays

int[] array1 = new int[] { 3, 5, 6, 9, 12, 14, 18, 20, 25, 28 };
int[] array2 = new int[] { 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 };

int count1 = array1.Length;
int count2 = array2.Length;
int[] arrayResult = new int[count1 + count2];

int a = 0, b = 0;   // indexes in origin arrays
int i = 0;          // index in result array

// join
while (a < count1 && b < count2)
{
    if (array1[a] <= array2[b])
    {
        // element in first array at current index 'a'
        // is less or equals to element in second array at index 'b'
        arrayResult[i++] = array1[a++];
    }
    else
    {
        arrayResult[i++] = array2[b++];
    }
}

// tail
if (a < count1)
{
    // fill tail from first array
    for (int j = a; j < count1; j++)
    {
        arrayResult[i++] = array1[j];
    }
}
else
{
    // fill tail from second array
    for (int j = b; j < count2; j++)
    {
        arrayResult[i++] = array2[j];
    }
}

// print result
Console.WriteLine("Result is {{ {0} }}", string.Join(",", arrayResult.Select(e => e.ToString())));