Simple Text File I/O
Simple Text File I/O
Many of the I/O tools provided by .NET are found in the System.IO namespace. One class that provides several general-purpose static methods related to file I/O is the File class. Two of the static methods provided by this class are:
The File.ReadAllText method takes a string as its only
parameter. This string should give the path to a text file. It will
then attempt to read that entire file and return its contents as a
string. For example, if fileName refers to a string containing
the path to a text file, then
string contents = File.ReadAllText(fileName);will read that entire file and place its contents into the string to
which contents refers. We can then process the string contents
however we need to.
The File.WriteAllText method takes two parameters:
- a string giving the path to a file; and
- a string? (i.e., a nullable string - a string that may be null) giving the text to be written.
It will then attempt to write the given text as the entire contents of
the given file. If this text is null, an empty file will be written. Thus, if fileName refers to a string containing
the path to a file and contents refers to some string, then
File.WriteAllText(fileName, contents);will write to that file the string to which contents refers.
When calling either of these methods, there are a number things that can go wrong. For example, the file might be accessed through a network, and access to the network might be lost before the method can complete. When such an issue prevents the successful completion of one of these methods, an exception is thrown. In the next section, we will discuss how to handle such exceptions.
While these methods are quite easy to use, they are not always the best ways of doing text file I/O. One drawback is that files can be quite large - perhaps too large to fit in memory or within a single string. Even when it is possible to read the entire file into a single string, it may use enough memory that performance suffers. In the section, “Advanced Text File I/O”, we will present other techniques for reading and writing text files.