tailieunhanh - Mastering Microsoft Visual Basic 2008 phần 6

Các tập tin đã luôn luôn là một khía cạnh quan trọng của chương trình. Chúng tôi sử dụng các tập tin để lưu trữ dữ liệu, và trong nhiều trường hợp chúng ta phải thao tác các tập tin và thư mục từ bên trong ứng dụng. Tôi không cần phải đưa ra ví dụ: | Chapter 15 Accessing Folders and Files Files have always been an important aspect of programming. We use files to store data and in many cases we have to manipulate files and folders from within applications. I need not give examples Just about any application that allows user input must store its data to a file or multiple files for later retrieval databases excluded of course. Manipulating files and folders is quite common too. Organizing files into folders and processing files en masse are two typical examples. I recently ran into a few web-related tasks that are worth mentioning here. A program for placing watermarks on pictures was the first. A watermark is a graphic that s placed over an image to indicate its origin. The watermark is transparent so it doesn t obscure the image but it makes the image unusable on any site other than the original one. You will see how to place a semitransparent graphic on top of an image in Chapter 19 Manipulating Images and Bitmaps and with the help of the information in this chapter you ll be able to scan a folder that has thousands of image files and to automate the process of watermarking the images. Another example has to do with matching filenames to values stored in a database. Product images are usually named after the product s ID and stored in separate files. There s a need for programs to match product IDs to images to find out whether there s an image for a specific product in the database or to simply move the image files around store the images for different product categories into different folders and so on . In this chapter you ll learn how to do the following Handle files with the My object Manipulate folders and files Save data to a file Monitor changes in the file system and react to them The IO Namespace and the FileSystem Component To manipulate folders and files as well as file input output I O operations the Framework provides the namespace. The My object provides .

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