Question

From the documentation of File.Move:

Note that if you attempt to replace a file by moving a file of the same name into that directory, you get an IOException. You cannot use the Move method to overwrite an existing file.

In short, you can’t overwrite on Move, so in order to facilitate overwriting on Move I mimic the behavior by doing a File.Copy followed by a File.Delete. Something like:

if (File.Exists(dstFileName))
{
    // System.IO.File.Move cannot be used to overwrite existing files, so we're going
    // to simulate that behavior with a Copy & Delete.
    File.Copy(procContext.FileName, dstFileName);
    File.Delete(procContext.FileName);
}
else
    File.Move(procContext.FileName, dstFileName);

My question is: Are there any situations that I need to guard against which could lead to the source file being deleted without it first being successfully copied?

My understanding from reading the documentation is that since File.Copy doesn’t return anything that it should throw an exception in any case that it doesn’t succeed. Has anyone encountered any situations where this isn’t true?

Answer 1

I suggest you to probe first if the target file exists and if yes, delete it. Then execute a normal move operation.

Since this sequence is not atomic, in case the destination exists you might want to rename it instead of deleting it, to avoid losing it in case the move fails.