ASP.NET PDF Viewer using C#, VB/NET

Almost all programmers have to deal with storing, retrieving, and processing information in files at some time or another. The .NET Framework provides a number of classes and methods we can use to find, create, read, and write files and directories In this chapter we ll look at some of the most common. Files, though, are just one example of a broader group of entities that can be opened, read from, and/or written to in a sequential fashion, and then closed. .NET defines a common contract, called a stream, that is offered by all types that can be used in this way. We ll see how and why we might access a file through a stream, and then we ll look at some other types of streams, including a special storage medium called isolated storage which lets us save and load information even when we are in a lower-trust environment (such as the Silverlight sandbox). Finally, we ll look at some of the other stream implementations in .NET by way of comparison. (Streams crop up in all sorts of places, so this chapter won t be the last we see of them they re important in networking, for example.)

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We, the authors of this book, have often heard our colleagues ask for a program to help them find duplicate files on their system. Let s write something to do exactly that. We ll pass the names of the directories we want to search on the command line, along with an optional switch to determine whether we want to recurse into subdirectories or not. In the first instance, we ll do a very basic check for similarity based on filenames and sizes, as these are relatively cheap options. Example 11-1 shows our Main function.

static void Main(string[] args) { bool recurseIntoSubdirectories = false; if (args.Length < 1) {

When inserting items in the middle of a very large list, use QLinkedList when constant time insertions and quick sequential access are required QVector is good at random access and when items are required to be stored in order in contiguous memory For queues and stacks, the QQueue and QStack classes work well; they offer quick insertion and access from the ends indicated by their name When you use a stack, you push and pop to the top; when you use a queue, you enqueue items on the tail and dequeue them from the head The QMap and QHash classes associate items with keys The QHash class sorts the items in an arbitrary order while performing slightly faster than the QMap class The map always sorts the items by key For managing several items per key, it is best to use the QMultiMap or QMultiHash classes.

}

ShowUsage(); return;

int firstDirectoryIndex = 0; if (args.Length > 1) { // see if we're being asked to recurse if (args[0] == "/sub") { if (args.Length < 2) { ShowUsage(); return; } recurseIntoSubdirectories = true; firstDirectoryIndex = 1; } } // Get list of directories from command line. var directoriesToSearch = args.Skip(firstDirectoryIndex); List<FileNameGroup> filesGroupedByName = InspectDirectories(recurseIntoSubdirectories, directoriesToSearch); DisplayMatches(filesGroupedByName); } Console.ReadKey();

Data binding is vital to any application, and how a programming language or framework implements data binding is a great gauge of its usefulness If the data binding APIs handle all the complexities of passing data around controls including reading, writing, and protecting data updates yet give you the flexibility you need to write your applications, then it s a winner In this circumstance Atlas is strong; it provides a rich declarative model that gives you powerful but easy-to-use data binding functionality In this chapter, you took a tour of the controls that are implemented in the Atlas libraries that give you a data binding API You started by looking at the nonvisual controls, which implement tables, records, views, filters, and the like You next moved on to the visual controls of ItemView and ListView and learned how you can use them to render bound data in the browser.

The basic structure is pretty straightforward. First we inspect the command-line arguments to work out which directories we re searching. Then we call InspectDirecto ries (shown later) to build a list of all the files in those directories. This groups the files by filename (without the full path) because we do not consider two files to be duplicates if they have different names. Finally, we pass this list to DisplayMatches, which displays any potential matches in the files we have found. DisplayMatches refines our test for duplicates further it considers two files with the same name to be duplicates only if they have the same size. (That s not foolproof, of course, but it s surprisingly effective, and we will refine it further later in the chapter.) Let s look at each of these steps in more detail. The code that parses the command-line arguments does a quick check to see that we ve provided at least one command-line argument (in addition to the /sub switch if present) and we print out some usage instructions if not, using the method shown in Example 11-2.

If you do not need to associate any items to a key but want to maintain a list of keys, the QSet class is right for you It works as a hash, but without any associated values..

private static void ShowUsage() { Console.WriteLine("Find duplicate files"); Console.WriteLine("===================="); Console.WriteLine( "Looks for possible duplicate files in one or more directories"); Console.WriteLine(); Console.WriteLine( "Usage: findduplicatefiles [/sub] DirectoryName [DirectoryName] ..."); Console.WriteLine("/sub - recurse into subdirectories"); Console.ReadKey(); }