try this logic
static void Main(string[] args)
{
int[] a = new int[] { 1, 2, 3, 4 };
int[] b = new int[] { 2,3, 5, 6 };
List<int> integerList = new List<int>();
List<int> integerListb = new List<int>();
int cnt = 0;
int k = 0;
int k1 = 0;
for (int i = 0; i < a.Count(); i++)
{
cnt = 0;
for (int j = 0; j < b.Count(); j++)
{
if (a[i] != b[j])
{
cnt++;
}
}
if (cnt == b.Count())
{
integerList.Add(a[i]);
Console.Write(integerList[k]);
k++;
}
}
for (int i = 0; i < b.Count(); i++)
{
cnt = 0;
for (int j = 0; j < a.Count(); j++)
{
if (b[i] != a[j])
{
cnt++;
}
}
if (cnt == a.Count())
{
integerListb.Add(b[i]);
Console.Write(integerListb[k1]);
k1++;
}
}
Console.Read();
}
}
</int></int></int></int>