converting bytes to a string C#

Question

I want to convert a binary file to a string which could be then converted back to the binary file. I tried this:

byte[] byteArray = File.ReadAllBytes(@"D:\pic.png");
for (int i = 0; i < byteArray.Length; i++)
{
    textBox1.Text += (char)byteArray[i];
}

but it's too slow, it takes about 20 seconds to convert 5KB on i5 CPU. I noticed that notepad does the same in much less time. Any ideas on how to do it?

Thanks

Jon Skeet · Accepted Answer · 2012-02-10 15:41:26Z

16

If you want to be able to convert back to binary without losing any information, you shouldn't be doing this sort of thing at all - you should use base64 encoding or something similar:

textBox1.Text = Convert.ToBase64String(byteArray);

You can then convert back using byte[] data = Convert.FromBase64String(text);. The important thing is that base64 converts arbitrary binary data to known ASCII text; all byte sequences are valid, all can be round-tripped, and as it only requires ASCII it's friendly to many transports.

There are four important things to take away here:

Don't treat arbitrary binary data as if it were valid text in a particular encoding. Phil Haack wrote about this in a blog post recently, in response to some of my SO answers.
Don't perform string concatenation in a loop; use a StringBuilder if you want to create one final string out of lots of bits, and you don't know how many bits in advance
Don't use UI properties in a loop unnecessarily - even if the previous steps were okay, it would have been better to construct the string with a loop and then do a single assignment to the Text property
Learn about System.Text.Encoding for the situation where you really have got encoded text; Encoding.UTF8.GetString(byteArray) would have been appropriate if this had been UTF-8-encoded data, for example

edited Feb 10, 2012 at 15:41

answered Feb 10, 2012 at 15:36

Jon Skeet

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3 Comments

Jon Skeet Over a year ago

@Brad: because you can then use Convert.FromBase64String to get it back again later...

Brad Over a year ago

So the idea is then just use the same encoding and the Base 64 is the most generic in comparsion to UTF8, 16, etc..?

Jon Skeet Over a year ago

@Brad: They're not the same thing. Encoding.UTF8 etc are used to represent arbitrary text as bytes... Base64 is used to represent arbitrary binary data as text.

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