You could use a Regex to check that it is “^[01]+$” (or better, “^[01]{1,32}$”), and then use Convert?
of course, exceptions are unlikely to be a huge problem anyway! Inelegant? maybe. But they work.
Example (formatted for vertical space):
static readonly Regex binary = new Regex("^[01]{1,32}$", RegexOptions.Compiled);
static void Main() {
Test("");
Test("01101");
Test("123");
Test("0110101101010110101010101010001010100011010100101010");
}
static void Test(string s) {
if (binary.IsMatch(s)) {
Console.WriteLine(Convert.ToInt32(s, 2));
} else {
Console.WriteLine("invalid: " + s);
}
}