Filesystem I/O

.NET provides two types that allow you to deal directly with files: File and FileInfo. A FileInfo instance represents an actual file and its metadata, but the File object contains only static methods used to manipulate files. That is, you must instantiate a FileInfo object to access the contents of the file as well as information about the file, but you can call File’s static methods to access files transiently.

The following C# code snippet shows how you can use FileInfo to determine the length of a file and its latest modification date. Note that both Length and LastAccessTime are properties of the FileInfo object:

// Create an instance of File and query it 
FileInfo fileInfo = new FileInfo(@"C:\data\file.xml");
long length = fileInfo.Length;
DateTime lastAccessTime = fileInfo.LastAccessTime;


Since the FileInfo and File types are contained in the System.IO namespace, to compile a class containing this code snippet you must include the following using statement:

using System.IO;

I skip the using statements in code snippets, but I include them in full code listings.

You can also use the File type to get the file’s last access time, but you cannot get the file’s length this way. The GetLastAccessTime( ) method returns the last access time for the filename passed to it, but there is no GetLength( ) method equivalent to the FileInfo object’s Length property:

// Get the last access time of a file transiently DateTime lastAccessTime = File.GetLastAccessTime(@"C:\data\file.xml"); ...

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