即使值更改，列表也会保持相同的第一个值

Question

I'm writing an encryptor code and to be more specific:
I'm currently writing a check that encrypts the letters and then decrypts them in order to see whether they can be, and then compares the decrypted output to the initial input.
I check this because the decryption formula uses cos^-1 which can't take use values.

Unfortunately, the list of the ints of the letters (a=1, b=2, z=26, etc) keeps adding the same first value, even though the value changes.

Part of the code:

foreach(int x in LetInt) {
    DoubInt++;

    try {
        CheckLetInt.Add(Convert.ToInt64(Math.Acos(Math.Pow((((Math.Tan((x+1) / (180/Math.PI)) / Math.Sin((x+1) / (180/Math.PI))) * (Math.Cos(A / (180/Math.PI)) * B)) - 1) / (Math.Cos(A / (180 / Math.PI)) * B), -1)) * (180 / Math.PI)));
        Console.WriteLine("Correct number:" + Convert.ToInt64(Math.Acos(Math.Pow((((Math.Tan((x+1) / (180/Math.PI)) / Math.Sin((x+1) / (180/Math.PI))) * (Math.Cos(A / (180/Math.PI)) * B)) - 1) / (Math.Cos(A / (180 / Math.PI)) * B), -1)) * (180 / Math.PI)));
        Console.WriteLine("List content:" + CheckLetInt[DoubInt - 1]);
        CheckLetter.Add(LetPos[Convert.ToInt64(CheckLetInt[DoubInt - 1]) - 1]);
    } catch(Exception) {
        ValueError.Visible = true;
        ClearAll();
        Console.WriteLine("Caught.");
    }
}

Output:

Anyone know what's going on?
The "Correct Number" and "List Content" formulae are the same.

Link to the project (it's a program so the code by itself doesn't work)

Link to the code by itself

Answer 1

Later down in the loop you do:

if(string.Join("", CheckLetter) == string.Join("", Letters.ToArray())) {
     ...
} else {
     ClearAll();
}

You never modify Letters in loop, but you do modify CheckLetter, so this will mostly return false, calling the ClearAll() method.

In ClearAll() you set DoubInt back to zero - hence always showing the first entry

        DoubInt = 0;

Note that this is not a good way to 'encrypt' anything. If you are just playing around then okay, but if you are trying to learn cryptography you should read up on same basics first if you think this is 'encryption'