File.Move Does Not Work - File Already Exists

问题:

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.

回答1:

You need to move it to another file (rather than a folder), this can also be used to rename.

Move:

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

Rename:

File.Move(@"c:\test\SomeFile.txt", @"c:\test\SomeFile2.txt");

The reason it says "File already exists" in your example, is because C:\test\Test tries to create a file Test without an extension, but cannot do so as a folder already exists with the same name.

回答2:

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.

回答3:

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
}

回答4:

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);

回答5:

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.

回答6:

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.

回答7:

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