System.Security.Cryptography.CryptographicException: Bad Data. in c#
===

I have decryption method to decrypt url data.

 public static string DecryptFromUrlParam(string inputString)
        {
            byte[] buffer = Convert.FromBase64String(inputString);
            TripleDESCryptoServiceProvider tripleDes = new TripleDESCryptoServiceProvider()
            {
                Key = Key,
                IV = IV
            };
            ICryptoTransform ITransform = tripleDes.CreateDecryptor();
            string decryptQueryString= Encoding.ASCII.GetString(ITransform.TransformFinalBlock(buffer, 0, buffer.Length));
            return DecodeURL(decryptQueryString);

           
        }

It gives following error:
"System.Security.Cryptography.CryptographicException: Bad Data. in c#"
Please give me solution for this error.