I have a list called com, which contains a bunch of integers. I need to check the list to make sure that each integer only exists once in the list.
So if:

```
com{1,2,3,4,1,3}

```

I need have some code to check that 1 is represented twice as well as 3.
This is my best guess on how to solve it:

```
for (int j = 0; j < com.Count; j++)
        {
            if (com.Contains(com[j]))
            {
                lion += 1;
            }
            else
            {
                lion = 0;
            }   
        }

```

But it doesn't work. Can anybody out there help me??