RSA Algorithem not working

Using RSA kye Encrypt and decrypt

<Encrypt>

byte[] EncryptedSymmetricKey;

RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();

 <decrypt>
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();string privateKey = "<RSAKeyValue><Modulus>66MHJalBW1TrRmO0xxNl7zcQiYfVtThRv/mAuXi/bKR7vRDZXd7wGXKWLt4NBTAQG37HQQuLgs2vhd5v66Mo7l8B+pits676y5uNE5x0NjTdV1ZH5VUHb9SBiZx1ldIINsTNB27OAdBo2z10jv0tf2GyBfcE7mj+JpNH ...