Converting a javascript method's functionality to C#

I have a javascript function that has functionality that I would like to convert to C#. I'm not sure how to properly translate this.

Can anyone help?

function validateSequenceNumber(val, num) {

   var seqNumber = ((parseFloat(num) + 0xCED9) * 0x8088405) & 0xFFFF
   var checksum = seqNumber.toString(16).toUpperC开发者_JAVA百科ase()

   if (checksum != val.substring(11, 15)) {
     return false;
   }
    return true;
   }

---

parseFloat becomes float.Parse, seqNumber.toString(16) becomes string.Format("{0:x}", seqNumber).ToUpper();

And note on substring parameters in C# are not start, end; rather start, length. So be careful. function becomes bool obviously. And I think that's it.

---

The string functions used should also use the invariant culture, since the function doesn't appear to be used for text display. Below is how the function might be converted:

 private static bool ValidateSequenceNumber(string val, string num) {
     System.Globalization.CultureInfo inv=System.Globalization.CultureInfo.InvariantCulture;
        int seqNumber = unchecked((((int)Double.Parse(num,System.Globalization.NumberStyles.Any,inv) + 0xCED9) * 0x8088405) & 0xFFFF);
        string checksum = seqNumber.ToString("X",inv).ToUpperInvariant();
        if (checksum != val.Substring(11, 4)) {
            return false;
        }
        return true;
    }

EDIT: Added Unchecked keyword: the overflow errors that would occur appear to be unimportant here.

---

public bool validateSequenceNumber(string val, int num)
{
    float seqNumber = (Int32)((Single.Parse(num) + 0xCED9) * 0x8088405) & 0xFFFF;
    string checksum = seqNumber.ToString("X").ToUpper();
    return (checksum != val.Substring(11, 4) ? false : true);
}