C# 4 and .NET 4

798 ❘ ChaPTer 29 mAnipulAtinG files And the reGistry
that you will be interested in: Add(), which adds a string to the collection, and CopyTo(), which copies the
string collection into a normal array (a System.Array instance). Each element of the StringCollection
object holds one line of the file.
The DisplayFile() method calls another method, ReadFileIntoStringCollection(), which actually
reads in the file. After doing this, you now know how many lines there are, so you are in a position to
copy the StringCollection into a normal, fixed-size array and feed it into the text box. Because only the
references to the strings, not the strings themselves, are copied when you actually make the copy, the process
is reasonably efficient:
void DisplayFile()
{
StringCollection linesCollection = ReadFileIntoStringCollection();
string [] linesArray = new string[linesCollection.Count];
linesCollection.CopyTo(linesArray, 0);
this.textBoxContents.Lines = linesArray;
}
code download ReadWriteText.sln
The second parameter of StringCollection.CopyTo() indicates the index within the destination array of
where you want the collection to start.
Now you examine the ReadFileIntoStringCollection() method. You use a StreamReader to read in
each line. The main complication here is the need to count the characters read in to make sure that you do
not exceed the capacity of the text box:
StringCollection ReadFileIntoStringCollection()
{
const int MaxBytes = 65536;
StreamReader sr = new StreamReader(chosenFile);
StringCollection result = new StringCollection();
int nBytesRead = 0;
string nextLine;
while ( (nextLine = sr.ReadLine()) != null)
{
nBytesRead += nextLine.Length;
if (nBytesRead > MaxBytes)
break;
result.Add(nextLine);
}
sr.Close();
return result;
}
That completes the code for this sample.
code download ReadWriteText.sln
If you run ReadWriteText, read in the Default.aspx file, and then save it, the file will be in Unicode
format. You would not be able to tell this from any of the usual Windows applications. Notepad, WordPad,
and even the ReadWriteText example will still read the file in and display it correctly under most versions
of Windows, although, because Windows 9x doesn’t support Unicode, applications like Notepad won’t be
able to understand the Unicode file on those platforms. (If you download the example from the Wrox Press
web site at www.wrox.com, you can try this!) However, if you try to display the file again using the earlier
BinaryFileReader sample, you can see the difference immediately, as shown in Figure 29-12. The two
initial bytes that indicate the file is in Unicode format are visible, and thereafter you see that every character
is represented by 2 bytes. This last fact is obvious because the high-order byte of every character in this
particular file is zero, so every second byte in this file now displays x00.
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