1. How do I return a base64 encoded string given a string?

  2. How do I decode a base64 encoded string into a string?

3

11 Answers

Encode

public static string Base64Encode(string plainText) { var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText); return System.Convert.ToBase64String(plainTextBytes); }

Decode

public static string Base64Decode(string base64EncodedData) { var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData); return System.Text.Encoding.UTF8.GetString(base64EncodedBytes); }
6

One liner code:

Note: Use System and System.Text directives.

Encode:

string encodedStr = Convert.ToBase64String(Encoding.UTF8.GetBytes("inputStr"));

Decode:

string inputStr = Encoding.UTF8.GetString(Convert.FromBase64String(encodedStr));
5

I'm sharing my implementation with some neat features:

  • uses Extension Methods for Encoding class. Rationale is that someone may need to support different types of encodings (not only UTF8).
  • Another improvement is failing gracefully with null result for null entry - it's very useful in real life scenarios and supports equivalence for X=decode(encode(X)).

Remark: Remember that to use Extension Method you have to (!) import the namespace with using keyword (in this case using MyApplication.Helpers.Encoding).

Code:

namespace MyApplication.Helpers.Encoding { public static class EncodingForBase64 { public static string EncodeBase64(this System.Text.Encoding encoding, string text) { if (text == null) { return null; } byte[] textAsBytes = encoding.GetBytes(text); return System.Convert.ToBase64String(textAsBytes); } public static string DecodeBase64(this System.Text.Encoding encoding, string encodedText) { if (encodedText == null) { return null; } byte[] textAsBytes = System.Convert.FromBase64String(encodedText); return encoding.GetString(textAsBytes); } } }

Usage example:

using MyApplication.Helpers.Encoding; // !!! namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Test1(); Test2(); } static void Test1() { string textEncoded = System.Text.Encoding.UTF8.EncodeBase64("test1..."); System.Diagnostics.Debug.Assert(textEncoded == "dGVzdDEuLi4="); string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded); System.Diagnostics.Debug.Assert(textDecoded == "test1..."); } static void Test2() { string textEncoded = System.Text.Encoding.UTF8.EncodeBase64(null); System.Diagnostics.Debug.Assert(textEncoded == null); string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded); System.Diagnostics.Debug.Assert(textDecoded == null); } } }
2

Based on the answers by Andrew Fox and Cebe, I turned it around and made them string extensions instead of Base64String extensions.

public static class StringExtensions { public static string ToBase64(this string text) { return ToBase64(text, Encoding.UTF8); } public static string ToBase64(this string text, Encoding encoding) { if (string.IsNullOrEmpty(text)) { return text; } byte[] textAsBytes = encoding.GetBytes(text); return Convert.ToBase64String(textAsBytes); } public static bool TryParseBase64(this string text, out string decodedText) { return TryParseBase64(text, Encoding.UTF8, out decodedText); } public static bool TryParseBase64(this string text, Encoding encoding, out string decodedText) { if (string.IsNullOrEmpty(text)) { decodedText = text; return false; } try { byte[] textAsBytes = Convert.FromBase64String(text); decodedText = encoding.GetString(textAsBytes); return true; } catch (Exception) { decodedText = null; return false; } } }
1

A slight variation on andrew.fox answer, as the string to decode might not be a correct base64 encoded string:

using System; namespace Service.Support { public static class Base64 { public static string ToBase64(this System.Text.Encoding encoding, string text) { if (text == null) { return null; } byte[] textAsBytes = encoding.GetBytes(text); return Convert.ToBase64String(textAsBytes); } public static bool TryParseBase64(this System.Text.Encoding encoding, string encodedText, out string decodedText) { if (encodedText == null) { decodedText = null; return false; } try { byte[] textAsBytes = Convert.FromBase64String(encodedText); decodedText = encoding.GetString(textAsBytes); return true; } catch (Exception) { decodedText = null; return false; } } } }

You can use below routine to convert string to base64 format

public static string ToBase64(string s) { byte[] buffer = System.Text.Encoding.Unicode.GetBytes(s); return System.Convert.ToBase64String(buffer); }

Also you can use very good online tool OnlineUtility.in to encode string in base64 format

1

URL safe Base64 Encoding/Decoding

public static class Base64Url { public static string Encode(string text) { return Convert.ToBase64String(Encoding.UTF8.GetBytes(text)).TrimEnd('=').Replace('+', '-') .Replace('/', '_'); } public static string Decode(string text) { text = text.Replace('_', '/').Replace('-', '+'); switch (text.Length % 4) { case 2: text += "=="; break; case 3: text += "="; break; } return Encoding.UTF8.GetString(Convert.FromBase64String(text)); } }
1
 using System; using System.Text; public static class Base64Conversions { public static string EncodeBase64(this string text, Encoding encoding = null) { if (text == null) return null; encoding = encoding ?? Encoding.UTF8; var bytes = encoding.GetBytes(text); return Convert.ToBase64String(bytes); } public static string DecodeBase64(this string encodedText, Encoding encoding = null) { if (encodedText == null) return null; encoding = encoding ?? Encoding.UTF8; var bytes = Convert.FromBase64String(encodedText); return encoding.GetString(bytes); } }

Usage

 var text = "Sample Text"; var base64 = text.EncodeBase64(); base64 = text.EncodeBase64(Encoding.UTF8); //or with Encoding 
// Encoding string passw = "tes123"; var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(passw); string pass = System.Convert.ToBase64String(plainTextBytes); // Normal var encodedTextBytes = Convert.FromBase64String(pass); string plainText = Encoding.UTF8.GetString(encodedTextBytes);

For those that simply want to encode/decode individual base64 digits:

public static int DecodeBase64Digit(char digit, string digit62 = "+-.~", string digit63 = "/_,") { if (digit >= 'A' && digit <= 'Z') return digit - 'A'; if (digit >= 'a' && digit <= 'z') return digit + (26 - 'a'); if (digit >= '0' && digit <= '9') return digit + (52 - '0'); if (digit62.IndexOf(digit) > -1) return 62; if (digit63.IndexOf(digit) > -1) return 63; return -1; } public static char EncodeBase64Digit(int digit, char digit62 = '+', char digit63 = '/') { digit &= 63; if (digit < 52) return (char)(digit < 26 ? digit + 'A' : digit + ('a' - 26)); else if (digit < 62) return (char)(digit + ('0' - 52)); else return digit == 62 ? digit62 : digit63; }

There are various versions of Base64 that disagree about what to use for digits 62 and 63, so DecodeBase64Digit can tolerate several of these.

You can display it like this:

var strOriginal = richTextBox1.Text; byte[] byt = System.Text.Encoding.ASCII.GetBytes(strOriginal); // convert the byte array to a Base64 string string strModified = Convert.ToBase64String(byt); richTextBox1.Text = "" + strModified;

Now, converting it back.

var base64EncodedBytes = System.Convert.FromBase64String(richTextBox1.Text); richTextBox1.Text = "" + System.Text.Encoding.ASCII.GetString(base64EncodedBytes); MessageBox.Show("Done Converting! (ASCII from base64)");

I hope this helps!