c# - Invalid length for a Base-64 char array error -

as title says, getting:

invalid length base-64 char array.

so doing construct email delivery using below method:

smsg += "<br><b>to complete registration, verify email</b>" + "<a href=" + siteurl + "?usenamw=" + encrypt(username.trim()) + "><br>here!</a>"; 

the encrypt method looks this:

private static string encrypt(string cleartext) {     string encryptionkey = "makv2spbni99212";     byte[] clearbytes = encoding.unicode.getbytes(cleartext);     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.createencryptor(), cryptostreammode.write))             {                 cs.write(clearbytes, 0, clearbytes.length);                 cs.close();             }             cleartext = convert.tobase64string(ms.toarray());         }     }     return cleartext; } 

here html looks in hotmail:

http://localhost:30850/activation.aspx?username=9mqkc5veebsl2qg6hbxl+r3kvnhoesig32op6eb6rd0=

on receiving end, activation.aspx.cs page has line:

string username = request.querystring["username"].tostring();     label1.text = decrypt(username); 

and decryption method:

private string decrypt(string ciphertext) {     string encryptionkey = "makv2spbni99212";     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; } 

so when input username foe example jonathan have no problem displaying jonathan on receiving end label. however, if input not multiple of 4 error. understand base64 takes in multiple of 4, if has 7 characters add space it. there solution this? thank much.

the base64 username string padded '=' @ end; ignored when url query string being interpreted. ie:

username => "9mqkc5veebsl2qg6hbxl+r3kvnhoesig32op6eb6rd0=" 

becomes:

username => 9mqkc5veebsl2qg6hbxl+r3kvnhoesig32op6eb6rd0 

in request handler.

you need url encode string before using in url.