Strings and Characters, Part 1 - 2.12 Decoding a Base64-Encoded Binary
(Page 12 of 12 )
Problem
You have a string that contains information such as a bitmap encoded as base64. You need to decode this data (which may have been embedded in an email message) from a string into a byte[] so that you can access the original binary.
Solution Using the static method Convert.FromBase64CharArray on the Convert class, an encoded char[] and/or string may be decoded to its equivalent byte[]:
using System;
public static byte[] Base64DecodeString(string inputStr)
{
byte[] decodedByteArray =
Convert.FromBase64CharArray(inputStr.ToCharArray(),
0, inputStr.Length);
return (decodedByteArray);
}
Discussion The static FromBase64CharArray method on the Convert class makes decoding an encoded base64 string a simple matter. This method returns a byte[] that contains the decoded elements of the string.
If you receive a file via email, such as an image file (.bmp), that has previously been converted to a string, to convert it back into its original bitmap file, you could do something like the following:
byte[] imageBytes = Base64DecodeString(bmpAsString);
fstrm = new FileStream(@"C:\winnt_copy.bmp", FileMode.CreateNew, FileAccess.Write);
BinaryWriter writer = new BinaryWriter(fstrm);
writer.Write(imageBytes);
writer.Close();
fstrm.Close();
In this code, the bmpAsString variable was obtained from the code in the Discussion section of Recipe 2.11. The imageBytes byte[] is the bmpAsString string converted back to a byte[], which can then be written back to disk.
To encode a byte[] to a string, see Recipe 2.13.
See Also See Recipe 2.11;see the “Convert.FromBase64CharArray Method” topic in the MSDN documentation.
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