How to find condition that start char in UTF-8 file is read, using FileStream and StreamReader? - c#-4.0

Question

In C# .NET 4.0 (really 4.5.2), my code reads a UTF-8 file.
FileStream fstream = new FileStream(path, FileMode.Open);
BufferedStream stream = new BufferedStream(fstream);
using (StreamReader reader = new StreamReader(stream, new UTF8Encoding())) {
int i;
while((i = reader.Read()) > -1) {
//a guess at a condition that is true I.F.F. reader has read character 1 of the file
if (stream.Position == (0 + sizeof(char)) || stream.Position == (0 + sizeof(int)) ) {
//while loop has reader read through all characters,
//but within this block, the reader has surely read character 1?
char c = (char)i;
}
}
reader.Close();
return 0;
}
I.F.F. we reach the condition that StreamReader reads the start character of the UTF-8 file, then run some function on the first character read.
With a FileStream and StreamReader used in reading a UTF-8 file, how do you know whether the aforementioned condition is met?
I am looking for an answer, please, that uses a property or method that already exists in the C# .NET 4.0 System.IO namespace. I thought use of the Stream.Position (BufferedStream.Position) property is the obvious way to find out where (i.e. at what character) in the file the reader is, but in trying a UTF-8 file that starts with some character in '0' to '9' (48 to 57), the loop with reader.Read() reads that char, and stream.Position = 43 . I don't know why 43 of all integral values is the value of stream.Position after the 1st character is read, or what the 43 means.
update: As the loop iterates and the reader reads more characters, the stream.Position value remains at 43. I don't know the Position property is useful then.

Answer 1

bool first = true;
while((i = reader.Read()) > -1)
{
if (first)
{
first = false;
// Do first character things
}
Note that the concept of first character is complex: what happens if the first glyph is è, that occupies two bytes in the file? The stream position will be at least 2 :-)
In general, you can check what the Position of the StreamReader.BaseStream is, but that Position is nearly useless, because there could be multiple levels of caching, or simply because for reading a single char, the StreamReader could have consumed 1-4 bytes (à is one byte, while some Unicode characters are long 4 bytes)... And then UTF8 files can have a BOM (an initial header long 3 bytes). That too is normally skipped from StreamReader.
Still, if you want, you can subclass the entire StreamReader class, overriding all the Read*, and keeping an internal flag SomethingHasBeenRead. It isn't difficult (everything is virtual in StreamReader)... It is only a little long to do.