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This This This This This This is is is is is is i: i: i: i: i: i: 1 2 3 4 5 6

Part I:

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lim [N ln N N + 1] = lim [N ln N N]

The program first creates a StringWriter called strwtr and outputs to it using WriteLine( ) Next, it creates a StringReader using the string contained in strwtr This string is obtained by calling ToString( ) on strwtr Finally, the contents of this string are read using ReadLine( )

The NET Framework defines a class called File that you will find useful when working with files because it contains several static methods that perform common file operations For example, File contains methods that copy or move a file, encrypt or decrypt a file, and delete a file It provides methods that obtain or set information about a file, such as whether it exists, its time of creation, its last access time, and its attributes (such as whether it is readonly, hidden, and so on) File also includes some convenience methods that let you read from a file and write to a file In addition, you can use a File method to open a file and obtain a FileStream reference to it Although File contains far too many methods to examine each one, we will look at three The first is Copy( ) and the other two are Exists( ) and GetLastAccessTime( ) These methods will give you an idea of the convenience that the File methods offer File is definitely a class that you will want to explore

one important way: it provides instance methods and properties rather than static methods to perform file operations Therefore, if you will be performing several file operations on the same file, then FileInfo might offer a more efficient solution

It occurred to me that I was missing some words in this sentence, and that without them my meaning was unclear Also, in this series, the word or should be used, not and

diverges, so the integral diverges N dx dx N (d) = lim = lim [arctan x]1 = 1 + x2 1 + x2 N + 1 N + 1 lim arctan N arctan 1 = = 2 4 4 N +

Earlier in this chapter you saw a program that copied a file by manually reading bytes from one file and writing them to another Although such a task is not particularly difficult, it can be fully automated by using the Copy( ) method defined by File It has the two versions shown here: static void Copy(string sourceFileName, string destFileName) static void Copy(string sourceFileName, string destFileName, boolean overwrite) Copy( ) copies the file specified by sourceFileName to the file specified by destFileName The first version copies the file only if destFileName does not already exist In the second form, if overwrite is passed true, the copy will overwrite the destination file if it exists Both can throw several types of exceptions, including IOException and FileNotFoundException The following program uses Copy( ) to copy a file Both the source and destination filenames are specified on the command line Notice how much shorter this version is than the copy program shown earlier It s also more efficient

/* Copy a file using FileCopy() To use this program, specify the name of the source file and the destination file For example, to copy a

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file called FIRSTDAT to a file called SECONDDAT, use the following command line:

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CopyFile FIRSTDAT SECONDDAT */ using System; using SystemIO; class CopyFile { static void Main(string[] args) { if(argsLength != 2) { ConsoleWriteLine("Usage: CopyFile From To"); return; } // Copy the files try { FileCopy(args[0], args[1]); } catch(IOException exc) { ConsoleWriteLine("Error Copying File\n" + excMessage); } } }

As you can see, this version of the program does not require that you create a FileStream or release resources The Copy( ) method handles all this for you Also notice that this version will not overwrite an existing file You might want to try using the second version of Copy( ), which does allow the destination to be overwritten

Using Exists( ) and GetLastAccessTime( )