File IO

StreamWriter buffers by writing data to an internal char array with a default size of 1024 (and a minimum size of 128). Once the buffer is full (or when you dispose the StreamWriter), it flushes the buffer to the underlying stream. You can change StreamWriter’s buffer size by passing in the bufferSize parameter. Here’s an … Read more

There are two ways to programmatically make a file read-only: Here’s an example showing both ways to make a file read-only: Using File.SetAttributes() is useful when you want to manage all of file’s attributes at once. FileAttributes is an enum flag, so you can use bitwise operations to add/remove multiple attributes at once. That’s why … Read more

When you want to set permissions for a directory (and its files/subdirectories), you can use DirectoryInfo.GetAccessControl() to get the directory’s security, add/modify/remove access control rules, and then use DirectoryInfo.SetAccessControl() to apply the changes. Access control rules are a complex combination of different settings. So before jumping into setting the permissions programmatically, I suggest taking a … Read more

The simplest way to delete a directory is by using Directory.Delete() (in System.IO). You specify the directory path (absolute or relative) and an optional parameter that tells it to delete everything in the directory. Here’s an example of how to use this to delete directories: Note: If you’re working with DirectoryInfo objects already, you can … Read more

You can use Directory.CreateDirectory() to create a directory at the specified path (absolute or relative), like this: This creates the directory if it doesn’t exist, otherwise it does nothing. That means you don’t need to check if the directory exists before calling Directory.CreateDirectory(). In this article, I’ll go into more details about using Directory.CreateDirectory(). CreateDirectory() … Read more

There are three ways to update a file’s content: Which option you pick depends on the file’s format and size. For example, if you’re writing to an existing CSV file, you’d append new lines to the end of the file. If you’re updating a JSON file, you’d read all the JSON content, make changes, then … Read more

You can use Directory.EnumerateFiles() (in System.IO) to search for files in a directory. This has many overloads, allowing you to specify exactly what you want. You can get all the files in a directory, get all files in all subdirectories, filter files by name (including extension), and filter by attributes. Here’s an example of getting … Read more

The simplest way to read a file is to use a high-level method in the .NET File API (in System.IO), such as File.ReadAllText(). These high-level methods abstract away the details of opening a file stream, reading it with StreamReader, and closing the file. Here’s an example of reading a text file’s content using File.ReadAllText(): Notice … Read more

There are a few ways to create a file and write to it using the .NET File API (in System.IO). The simplest way is to use high-level methods like File.WriteAllText() and File.WriteAllLines(), specifying the file path and string(s) to write to the file. Here’s an example of using these (and their async equivalents): These high-level … Read more

You can use System.IO.File.Delete() to delete a file by specifying its relative or absolute path. Here’s an example: Note: Unlike other methods in the File API, there’s no async version of File.Delete(). If the specified file exists and the permissions are right, then File.Delete() deletes the file as expected. If there’s a problem, it throws … Read more

The simplest way to save a list of strings to a file is to use File.WriteAllLines(). This creates (or overwrites) the specified file and writes each string on a new line. The resulting file looks like this: Note: Showing non-printable newline characters \r\n for clarity. Specifying the separator character What if you want to separate … Read more

This article shows how to get a file’s checksum using any of these hashing algorithms: MD5, SHA1, SHA256, SHA384, and SHA512. If you are only interested getting a specific type of checksum, take a look at the first section. If you’re interested in a general-purpose checksum method that allows you to generate the checksum using … Read more

.NET has a good, high-level File API that abstracts away the complexity of file operations. You can create, read, update, delete, and search for files with a single method call in most scenarios. The File API is located in the System.IO namespace. Here’s a brief example of creating a new file with content, reading its … Read more

Let’s say you want to search the file system and find all empty directories. An empty directory has the following conditions: To check if a directory is empty, you have to recursively check all of its subdirectories for any files. Use Directory.EnumerateDirectories() to loop through a directory’s immediate subdirectories, and use Directory.EnumerateFiles().Any() to check for … Read more

You can use the FileSystemWatcher class to detect file system changes, such as when a file is created, deleted, modified, or renamed. When a change happens, it raises an event that you can handle. This is an event-based alternative to polling for file changes. In this article, I’ll show how to use FileSystemWatcher to detect … Read more