What is the difference between FileMode.Create and FileMode.Truncate?

user_11397900 0
Viewed 3391

I don't really understand it:

FileMode.Create creates a new file if it doesn't exists, or overwrites one if it does.

FileMode.Truncate doesn't create a new file, but deletes the entire content of an existing one, so basically it also overwrites the file.

So why is there even the possibility to do:

public void DoStuff()
{
    using (FileStream fs = File.Open(path, FileMode.Truncate, FileAccess.Write, FileShare.None))
    {
        //Do something
    }
}

When it's enough to do:

public void DoStuff()
{
    using (FileStream fs = File.Open(path, FileMode.Create, FileAccess.Write, FileShare.None))
    {
        //Do something
    }
}

Because both are basically using an empty file to write stuff into it

c#
2 Answers

For FileMode.Truncate file must exist. If it doesn't you'll get an exception. FileMode.Create would create new file in this case.

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user_43121320

The question sounds like both options might be needed at the same time:

  • if an old file is there, truncate it;
  • if it is not there, create a new one.

My solution to this:

public void DoStuff()
{
    var fileInfo = new FileInfo(path);
    var fileMode = fileInfo.Exists ? FileMode.Truncate : FileMode.CreateNew;
    using (FileStream fs = File.Open(path, fileMode, FileAccess.Write, FileShare.None))
    {
        //Do something
    }
}
user_44178110
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