Question

My andgate works when I use just 1 bit strings, but anything else, it doesn’t work at all and tells me “Specific argument was out of the range of valid values. Parameter name: startIndex.”

Anyone know what I’m doing wrong here? And is there a better way to add to the end of a string? Thanks!

private string parsestrings(string s1, string s2)
{
    int n = s1.Length;
    int m = s2.Length;
    int l;
    string s = "";
    if (n > m)
    {
        for(int i = 0; i <= n; i++)
        {
            l = AndGate(s1[i], s2[i]);
            s.Insert(i, IntToBinary(l));
        }
    }
    else
    {
        for (int i = 0; i <= n; i++)
        {
            l = AndGate(s1[i], s2[i]);
            s.Insert(i, IntToBinary(l));
        }
    }
    return s;
}

private int AndGate(int m, int n)
{
    if (m == 1 && n == 1)
        return 1;
    if (m == 1 && n == 0)
        return 0;
    if (m == 0 && n == 1)
        return 0;
    else
        return 0;
}

Answer 1

Your logic seems a little off. If n > m, then the loop should probably stop at m instead of n:

for(int i = 0; i <= m; i++)
{
    l = AndGate(s1[i], s2[i]);
    s.Insert(i, IntToBinary(l));
}

The second loop seems right, though.

A second thought is that the condition i <= m should probably be i < m, since s1[m] is one character past the string.

Finally, you can either follow spender’s advice, or use a StringBuilder instead. It’s generally better for constructing a string than continually adding to and updating a string.