System.IO.File class provides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects.
The System.IO.StreamWriter class implements a TextWriter for writing characters to a stream in a particular encoding.
The following code examples show how to write text to a text file.

The first example shows how to add text to an existing file. The second example shows how to create a new text file and write a string to it. Similar functionality can be provided by the WriteAllText methods.