This is the second part of a C# File I/O series. Last week, you learned a synchronous method for writing to a file. This week, you will learn how to asynchronously write to a text file in C# using the StreamWriter constructor within an async method.
Writing to a file asynchronously allows your application to continue executing other tasks while the file is being written. This is helpful when writing large amounts of data or when you will not need to read content from the file immediately.
Performing read/write operations asynchronously is useful with GUI applications, because the program’s user-interface can still be redrawn (if window is resized, for example), while the file I/O operation is being completed. The technique is also useful in applications where performance is important, such as when developing ASP.NET web apps.
Click through to the source to learn how: Source