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ASP.NET Session 7
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ASP.NET Session 7

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Transcript

  • 1. File Program Session 7
  • 2. Objectives  File Namespace.  Working with file classes.  StreamWriters and StreamReaders.  Read & Write file handling program.
  • 3. Introduction • Reading and writing files are essential aspects of many .NET applications. • Files can be a great way to store data using the .net application, or they can be used to transfer data between applications.
  • 4. STREAMS • All input and output in the .NET Framework involve the use of streams. • A stream is an abstract representation of a serial device. • A serial device is something that stores data in a linear manner and is accessed the same way: one byte at a time. • This device can be a disk file, a network channel, a memory location, or any other object that supports reading and writing to it in a linear manner.
  • 5. There are two types of streams: Output:  Output streams are used when data is written to some external destination.  External destination: a physical disk file, a network location, a printer, or another program. Input:  Input streams are used to read data into memory or variables that your program can access.  An input stream can come from almost any source
  • 6. THE CLASSES FOR INPUT &OUTPUT • The System.IO namespace contains almost all of the classes for read & write operation. • few classes are contained in System.IO. CLASS File Directory Path StreamReader StreamWriter
  • 7. The File and Directory Classes • The File and Directory utility classes expose many static methods for manipulating. • File classes have some method METHOD DESCRIPTION Copy() Copies a file from a source location to a target location. Create() Creates a file in the specified path. Delete() Deletes a file. Open() Returns a FileStream object at the specified path. Move() Moves a specified file to a new location. You can specify a different name for the file in the new location.
  • 8. Directory classes have some method Path Names and Relative Paths:  When specifying a path name in .NET code, you can use either absolute or relative path names. • An absolute path name explicitly specifies a file or directory from a known location — such as the C: drive. • C:WorkLogFile.txt — this path defines exactly where the file is, with no ambiguity. Method Description CreateDirectory() Creates a directory with the specified path. Delete() Deletes the specified directory and all the files within it.
  • 9.  Relative path names are relative to a starting location.  By using relative path names, no drive or known location needs to be specified. • The current working directory was the starting point, which is the default behavior for relative path names. • For example, if your application is running in the C:DevelopmentFileDemo directory and uses the relative path LogFile.txt, the file references would be C:DevelopmentFileDemoLogFile.txt.
  • 10. The StreamWriter Object • The StreamWriter class enables you to write characters and strings to a file. • The StreamWriter class handles the writing to the FileStream object. FileStream aFile = new FileStream("Log.txt", FileMode.CreateNew); StreamWriter sw = new StreamWriter(aFile); • A StreamWriter object can also be created directly from a file: StreamWriter sw = new StreamWriter("Log.txt", true);
  • 11. • If this is set to false, then a new file is created or the existing file is truncated and then opened. • If it is set to true, then the file is opened and the data is retained. If there is no file, then a new one is created.
  • 12. The StreamReader Object Input streams are used to read data from an external source. StreamReader objects are created in much the same way as StreamWriter objects.
  • 13. The StreamReader Object Input streams are used to read data from an external source. StreamReader objects are created in much the same way as StreamWriter objects.
  • 14. • StreamReader objects are created in much the same way as StreamWriter objects. • FileStream aFile = new FileStream("Log.txt", FileMode.Open); • StreamReader sr = new StreamReader(aFile); • The StreamReader class can be created directly from a string containing the path to a particular file: • StreamReader sr = new StreamReader("Log.txt");
  • 15. Summary • File program concept. • Several property of System.IO Namespace. • Stream concept • StreamWriter & StreamReader.

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