invalid length for base-64 char array or string c#

public string Decrypt(string cipherText)

{

string EncryptionKey = "Your Salt Key";// Change With your Encryption Key

byte[] cipherBytes = Convert.FromBase64String(cipherText);

using (Aes encryptor = Aes.Create())

{

Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

encryptor.Key = pdb.GetBytes(32);

encryptor.IV = pdb.GetBytes(16);

using (MemoryStream ms = new MemoryStream())

{

using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))

{

cs.Write(cipherBytes, 0, cipherBytes.Length);

cs.Close();

}

cipherText = Encoding.Unicode.GetString(ms.ToArray());

}

}

return cipherText;

}

 

Hope it works, Thanks