How to GetBytes() in C# with UTF8 encoding with BOM?

Question

I'm having a problem with UTF8 encoding in my asp.net mvc 2 application in C#. I'm trying let user download a simple text file from a string. I am trying to get bytes array with the following line:

var x = Encoding.UTF8.GetBytes(csvString);

but when I return it for download using:

return File(x, ..., ...);

I get a file which is without BOM so I don't get Croatian characters shown up correctly. This is because my bytes array does not include BOM after encoding. I triend inserting those bytes manually and then it shows up correctly, but that's not the best way to do it.

I also tried creating UTF8Encoding class instance and passing a boolean value (true) to its constructor to include BOM, but it doesn't work either.

Anyone has a solution? Thanks!

Answer 1

Try like this:

public ActionResult Download() {     var data = Encoding.UTF8.GetBytes("some data");     var result = Encoding.UTF8.GetPreamble().Concat(data).ToArray();     return File(result, "application/csv", "foo.csv"); } 

The reason is that the UTF8Encoding constructor that takes a boolean parameter doesn't do what you would expect:

byte[] bytes = new UTF8Encoding(true).GetBytes("a"); 

The resulting array would contain a single byte with the value of 97. There's no BOM because UTF8 doesn't require a BOM.

Answer 2

I created a simple extension to convert any string in any encoding to its representation of byte array when it is written to a file or stream:

public static class StreamExtensions {     public static byte[] ToBytes(this string value, Encoding encoding)     {         using (var stream = new MemoryStream())         using (var sw = new StreamWriter(stream, encoding))         {             sw.Write(value);             sw.Flush();             return stream.ToArray();         }     } } 

Usage:

stringValue.ToBytes(Encoding.UTF8) 

This will work also for other encodings like UTF-16 which requires the BOM.