5 ways to write to a file with C# .NET

It’s a common scenario that you need to write some content to a file. Here you see 5 ways to achieve that.

1. Using a FileStream:

private void WriteToAFileWithFileStream()
{
	using (FileStream target = File.Create(@"c:\mydirectory\target.txt"))
	{
		using (StreamWriter writer = new StreamWriter(target))
		{
			writer.WriteLine("Hello world");
		}
	}
}

This will create a new file or overwrite an existing one.

Write and WriteLine have asynchronous versions as well: WriteAsync and WriteLineAsync. If you don’t know how to use async methods that return a Task then start here.

The following variation will append the text to an existing file or create a new one:

using (FileStream target = File.Open(@"c:\mydirectory\target2.txt", FileMode.Append, FileAccess.Write))
{
	using (StreamWriter writer = new StreamWriter(target))
	{
		writer.WriteLine("Hello world");
	}
}

2. Using a StreamWriter directly – to be used for text files:

private static void WriteToAFileWithStreamWriter()
{
	using (StreamWriter writer = File.CreateText(@"c:\mydirectory\target.txt"))
	{
		writer.WriteLine("Bye world");
	}
}

This will create a new file or overwrite an existing one.

The following variation will append the text to an existing file or create a new one:

using (StreamWriter writer = File.AppendText(@"c:\mydirectory\target.txt"))
{
	writer.WriteLine("Bye world");
}

3. Using File:

private static void WriteToAFileWithFile()
{
	File.WriteAllText(@"c:\mydirectory\target.txt", "Hello again World");
}

There’s File.WriteAllBytes as well if you have the contents as a byte array. There’s also a File.AppendAllText method to append to an existing file or create a new one if it doesn’t exist.

4. Using a MemoryStream first:

private static void WriteToAFileFromMemoryStream()
{
	using (MemoryStream memory = new MemoryStream())
	{
		using (StreamWriter writer = new StreamWriter(memory))
		{
			writer.WriteLine("Hello world from memory");
			writer.Flush();
			using (FileStream fileStream = File.Create(@"c:\mydirectory\memory.txt"))
			{
				memory.WriteTo(fileStream);
			}
		}
	}
}

5. Using a BufferedStream:

private static void WriteToAFileFromBufferedStream()
{
	using (FileStream fileStream = File.Create(@"c:\mydirectory\buffered.txt"))
	{
		using (BufferedStream buffered = new BufferedStream(fileStream))
		{
			using (StreamWriter writer = new StreamWriter(buffered))
			{
				writer.WriteLine("Hello from buffered.");
			}
		}
	}
}

Read all posts dedicated to file I/O here.

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About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

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