Encoding strings to and from base-64

Question

I'm trying to encode some strings back and forth from base-64 string and I'm having truble to get the right result.

string text = base64string.... //Here I have a base-64 string.
byte[] encodedByte = System.Text.ASCIIEncoding.ASCII.GetBytes(text);
string base64Encoded = Convert.ToBase64String(encodedByte);

if (text == base64Encoded) //If the new encoded string is equal to its original value
    return base64Encoded;

I have tried my ways to do this and I don't seem to get the right result. I have tried both with System.Text.Encoding.Unicode and System.Text.Encoding.UTF8

What could be the problem? Does anyone have a proper solution?

Answer 1

string text = base64string.... //Here I have a base-64 string.
byte[] encodedByte = System.Text.ASCIIEncoding.ASCII.GetBytes(text);
string base64Encoded = Convert.ToBase64String(encodedByte);

You are double encoding the string. You begin with a base64 string, get the bytes, and then encode it again . If you want to compare you will need to begin with the original string.

Answer 2

If text is a base-64 string, then you are doing it backwards:

byte[] raw = Convert.FromBase64String(text); // unpack the base-64 to a blob
string s = Encoding.UTF8.GetString(raw); // assume the blob is UTF-8, and 
                                         // decode to a string

which will get you it as a string . Note, though, that this scenario is only useful for representing unicode text in an ascii format. Normally you wouldn't base-64 encode it if the original contents are string .

Answer 3

Convert whatever it is that you need in Base64 into a Byte array then use the FromBase64String and ToBase64String to convert to and from Base64:

Byte[] buffer = Convert.FromBase64String(myBase64String1);
myBase64String2 = Convert.ToBase64String(buffer);

myBase64String1 will be equal to myBase64String2. You will need to use other methods to get your data type into a Byte array and the reverse to get your data type back. I have used this to convert the content of a class into a byte array and then to Base64 string and write the string to the filesystem. Later I read it back into a class instance by reversing the process.

Answer 4

You have the encoding code correctly laid out. To confirm whether the base64-encoded string is correct, you can try decoding it and comparing the decoded contents to the original:

var decodedBytes = Convert.FromBase64String(base64encoded);
var compareText = System.Text.Encoding.ASCII.GetString(decodedText);

if (text == compareText)
{
    // carry on...
    return base64encoded;
}