Question

Both StreamReader and BinaryReader can be used to get data from binary file ( for example )

BinaryReader :

   using (FileStream fs = File.Open(@"c:\1.bin",FileMode.Open))
            {
                    byte[] data = new BinaryReader(fs).ReadBytes((int)fs.Length);
                    Encoding.getstring....
            }

StreamReader :

  using (FileStream fs = File.Open(@"c:\1.bin",FileMode.Open))
            {
                using (StreamReader sr = new StreamReader(fs,Encoding.UTF8))
                {
                       var myString=sr.ReadToEnd();
                }
            }

What is the difference and when should I use which ?

Answer 1

Both StreamReader and BinaryReader can be used to get data from binary file

Well, StreamReader can be used to get text data from a binary representation of text.

BinaryReader can be used to get arbitrary binary data. If some of that binary data happens to be a representation of text, that’s fine – but it doesn’t have to be.

Bottom line:

• If the entirety of your data is a straightforward binary encoding of text data, use StreamReader.
• If you’ve fundamentally got binary data which may happen to have some portions in text, use BinaryReader

So for example, you wouldn’t try to read a JPEG file with StreamReader.