[c#] File.Move Does Not Work - File Already Exists

I've got a folder:

c:\test

I'm trying this code:

File.Move(@"c:\test\SomeFile.txt", @"c:\test\Test");

I get exception:

File already exists

The output directory definitely exists and the input file is there.

This question is related to c# file-io

The answer is


You can do a P/Invoke to MoveFileEx() - pass 11 for flags (MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH)

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Unicode)]
static extern bool MoveFileEx(string existingFileName, string newFileName, int flags);

Or, you can just call

Microsoft.VisualBasic.FileIO.FileSystem.MoveFile(existingFileName, newFileName, true);

after adding Microsoft.VisualBasic as a reference.


What you need is:

if (!File.Exists(@"c:\test\Test\SomeFile.txt")) {
    File.Move(@"c:\test\SomeFile.txt", @"c:\test\Test\SomeFile.txt");
}

or

if (File.Exists(@"c:\test\Test\SomeFile.txt")) {
    File.Delete(@"c:\test\Test\SomeFile.txt");
}
File.Move(@"c:\test\SomeFile.txt", @"c:\test\Test\SomeFile.txt");

This will either:

  • If the file doesn't exist at the destination location, successfully move the file, or;
  • If the file does exist at the destination location, delete it, then move the file.

Edit: I should clarify my answer, even though it's the most upvoted! The second parameter of File.Move should be the destination file - not a folder. You are specifying the second parameter as the destination folder, not the destination filename - which is what File.Move requires. So, your second parameter should be c:\test\Test\SomeFile.txt.


Try Microsoft.VisualBasic.FileIO.FileSystem.MoveFile(Source, Destination, True). The last parameter is Overwrite switch, which System.IO.File.Move doesn't have.


If file really exists and you want to replace it use below code:

string file = "c:\test\SomeFile.txt"
string moveTo = "c:\test\test\SomeFile.txt"

if (File.Exists(moveTo))
{
    File.Delete(moveTo);
}

File.Move(file, moveTo);

According to the docs for File.Move there is no "overwrite if exists" parameter. You tried to specify the destination folder, but you have to give the full file specification.

Reading the docs again ("providing the option to specify a new file name"), I think, adding a backslash to the destination folder spec may work.


Personally I prefer this method. This will overwrite the file on the destination, removes the source file and also prevent removing the source file when the copy fails.

string source = @"c:\test\SomeFile.txt";
string destination = @"c:\test\test\SomeFile.txt";

try
{
    File.Copy(source, destination, true);
    File.Delete(source);
}
catch
{
    //some error handling
}

1) With C# on .Net Core 3.0 and beyond, there is now a third boolean parameter:

see https://docs.microsoft.com/en-us/dotnet/api/system.io.file.move?view=netcore-3.1

In .NET Core 3.0 and later versions, you can call Move(String, String, Boolean) setting the parameter overwrite to true, which will replace the file if it exists.

2) For all other versions of .Net, https://stackoverflow.com/a/42224803/887092 is the best answer. Copy with Overwrite, then delete the source file. This is better because it makes it an atomic operation. (I have attempted to update the MS Docs with this)


If you don't have the option to delete the already existing file in the new location, but still need to move and delete from the original location, this renaming trick might work:

string newFileLocation = @"c:\test\Test\SomeFile.txt";

while (File.Exists(newFileLocation)) {
    newFileLocation = newFileLocation.Split('.')[0] + "_copy." + newFileLocation.Split('.')[1];
}
File.Move(@"c:\test\SomeFile.txt", newFileLocation);

This assumes the only '.' in the file name is before the extension. It splits the file in two before the extension, attaches "_copy." in between. This lets you move the file, but creates a copy if the file already exists or a copy of the copy already exists, or a copy of the copy of the copy exists... ;)