c# - Invalid length for Convert.FromBase64String -

so i'm trying decrypt encrypted string, encrypts fine, , decrypts if i'm lucky enough string length long.. firstly here code called decryption method

decrypted = decrypt(recieved, getstring(anarchyaes.key)); addtochat(decrypted); 

recieved encrypted string, , other parameter decryption key. here decrypt method..

public static string decrypt(string cipherstring, string securitykey)     {         var key = securitykey;         var keyarray = encoding.utf8.getbytes(key);          var tdes = new tripledescryptoserviceprovider         {             key = keyarray,             mode = ciphermode.ecb,             padding = paddingmode.pkcs7         };          var ctransform = tdes.createdecryptor();         var toencryptarray = convert.frombase64string(cipherstring);         var resultarray = ctransform.transformfinalblock(toencryptarray, 0, toencryptarray.length);         tdes.clear();         return encoding.utf8.getstring(resultarray);     } 

it fails when does

var toencryptarray = convert.frombase64string(cipherstring); 

when string more 7 characters giving error, invalid length 64 base string. i'm wondering how possibly fix this, insight appreciated.

encrpytion code:

public static string encrypt(string toencrypt, string securitykey)         {             var key = securitykey;             var keyarray = encoding.utf8.getbytes(key);              var tdes = new tripledescryptoserviceprovider             {                 key = keyarray,                 mode = ciphermode.ecb,                 padding = paddingmode.pkcs7             };              var ctransform = tdes.createencryptor();             var toencryptarray = encoding.utf8.getbytes(toencrypt);             var resultarray = ctransform.transformfinalblock(toencryptarray, 0, toencryptarray.length);             tdes.clear();             return convert.tobase64string(resultarray, 0, resultarray.length);         }