Is a random string good for an AES-256 instance

Question

I have a randomly generated string of about 256 characters long. This string is hashed to for a key and initialization vector for a program running on the .NET framework 4.8. Is this method secure from a professional point of view?

Answer 1

The Following Code Is Now Using The Password Derive Bytes Function, All Values Will Be Changed Accordingly

    string Password = "Example";
    byte[] IV = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
    byte[] Salt = Encoding.ASCII.getBytes("Salt Example");
    PasswordDeriveBytes pdb = new PasswordDerivedBytes(Password,Salt);
    Aes Alg = Aes.Create();
    Alg.Key = pdb.CryptDeriveKey("Aes","SHA256",256,IV);
    Alg.IV = IV;

The Code Above Is C#