CODEWITHSUNDEEP
c#.net
Paul Hollingsworth
Paul Hollingsworth

Reputation: 13374

Creating an empty file in C#

What's the simplest/canonical way to create an empty file in C#/.NET?

The simplest way I could find so far is:

System.IO.File.WriteAllLines(filename, new string[0]);

Upvotes: 225

Views: 209049

Answers (7)

Jon Skeet
Jon Skeet

Reputation: 1501163

Using just File.Create will leave the file open, which probably isn't what you want.

You could use:

// Results in compiler warning "warning CS0642: Possible mistaken empty statement"
using (File.Create(filename)) ;

That looks slightly odd, mind you. You could use braces instead:

using (File.Create(filename)) {}

Or just call Dispose directly:

File.Create(filename).Dispose();

Either way, if you're going to use this in more than one place you should probably consider wrapping it in a helper method, e.g.

public static void CreateEmptyFile(string filename)
{
    File.Create(filename).Dispose();
}

Note that calling Dispose directly instead of using a using statement doesn't really make much difference here as far as I can tell - the only way it could make a difference is if the thread were aborted between the call to File.Create and the call to Dispose. If that race condition exists, I suspect it would also exist in the using version, if the thread were aborted at the very end of the File.Create method, just before the value was returned...

Upvotes: 452

Phil Haselden
Phil Haselden

Reputation: 3006

To avoid accidentally overwriting an existing file use:

using (new FileStream(filename, FileMode.CreateNew)) {}

...and handle the IOException which will occur if the file already exists.

File.Create, which is suggested in other answers, will overwrite the contents of the file if it already exists. In simple cases you could mitigate this using File.Exists(). However something more robust is necessary in scenarios where multiple threads and/or processes are attempting to create files in the same folder simultaneously.

Upvotes: 8

Tamas Czinege
Tamas Czinege

Reputation: 121334

File.WriteAllText("path", String.Empty);

or

File.CreateText("path").Close();

Upvotes: 45

aggieNick02
aggieNick02

Reputation: 2777

A somewhat common use case for creating an empty file is to trigger something else happening in a different process in the absence of more sophisticated in process communication. In this case, it can help to have the file creation be atomic from the outside world's point of view (particularly if the thing being triggered is going to delete the file to "consume" the trigger).

So it can help to create a junk name (Guid.NewGuid.ToString()) in the same directory as the file you want to create, and then do a File.Move from the temporary name to your desired name. Otherwise triggered code which checks for file existence and then deletes the trigger may run into race conditions where the file is deleted before it is fully closed out.

Having the temp file in the same directory (and file system) gives you the atomicity you may want. This gives something like.

public void CreateEmptyFile(string path)
{
    string tempFilePath = Path.Combine(Path.GetDirectoryName(path),
        Guid.NewGuid.ToString());
    using (File.Create(tempFilePath)) {}
    File.Move(tempFilePath, path);
}

Upvotes: 3

umilmi81
umilmi81

Reputation: 136

You can chain methods off the returned object, so you can immediately close the file you just opened in a single statement.

File.Open("filename", FileMode.Create).Close();

Upvotes: 3

Eoin Campbell
Eoin Campbell

Reputation: 44288

System.IO.File.Create(@"C:\Temp.txt");

As others have pointed out, you should dispose of this object or wrap it in an empty using statement. 

using (System.IO.File.Create(@"C:\Temp.txt"));

Upvotes: 24

Crippledsmurf
Crippledsmurf

Reputation: 4012

Path.GetTempFileName() will create a uniquly named empty file and return the path to it.

If you want to control the path but get a random file name you can use GetRandomFileName to just return a file name string and use it with Create

For example:

string fileName=Path.GetRandomFileName();
File.Create("custom\\path\\" + fileName);

Upvotes: 0

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