Find the difference of two folders and delete files

Question

I have two folders : FolderA and FolderB I want to delete the files in FolderA which also exist in FolderB. (i.e. Common files will be deleted from folderA)

How can I do this most efficiently in C#? (That's a critical point in the project and it has to be as efficient as possible )

Thanx

Are files considered equal if they have equal file name or are the other parameters (such as size, attributes etc.) also compared? — Ivan Golović, Dec 19 '12 at 08:44
Nothing needs to be compared, the files are equal if filenames are equal — EngelbertCoder, Dec 19 '12 at 08:49

score 2 · Answer 1 · answered Dec 19 '12 at 08:48

2

You can do this with the help of LINQ. See here.

answered Dec 19 '12 at 08:48

d.moncada

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Tim Schmelter · Accepted Answer · 2012-12-19T08:57:02.633

2

This is easy, readable and also efficient:

var common = from f1 in Directory.EnumerateFiles(folderA, "*.*", SearchOption.AllDirectories)
             join f2 in Directory.EnumerateFiles(folderB, "*.*", SearchOption.AllDirectories)
             on Path.GetFileName(f1) equals Path.GetFileName(f2)
             select f1;

foreach (string file in common)
{
    File.Delete(file);
}

Assuming that you just want to compare the file names (and extension).

edited Dec 19 '12 at 08:57

answered Dec 19 '12 at 08:49

Tim Schmelter

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I am not so familiar with that syntax but it looks very compact. How can we extend it efficiently so that to delete both of the files(both on f1 and f2)? – EngelbertCoder Dec 19 '12 at 09:24
@EngelbertCoder: Then you need to use an anonymous type. Here's the code-difference: `select new { File1 = f1, File2 = f2 }; foreach (var files in common) { File.Delete(files.File1); File.Delete(files.File2); }`. Btw, that's the Linq query syntax. You could also use the [method syntax](http://msdn.microsoft.com/en-us/library/system.linq.enumerable.join.aspx) but i prefer queries with `Joins`. – Tim Schmelter Dec 19 '12 at 09:31
@EngelbertCoder: [**Here**](http://stackoverflow.com/questions/5551264/why-is-linq-join-so-much-faster-than-linking-with-where) are some infos on `Join` and it's performance. – Tim Schmelter Dec 19 '12 at 09:38

Ivan Golović · Answer 3 · 2012-12-19T08:57:42.870

2

If you only want to compare file names, here is how you can do it, I did a quick test of this code and it works:

        string pathA = @"C:\New FolderA";
        string pathB = @"C:\New FolderB";

        var filesA = Directory.GetFiles(pathA).Select(path => Path.GetFileName(path));
        var filesB = Directory.GetFiles(pathB).Select(path => Path.GetFileName(path));

        var toBeDeleted = filesA.Intersect(filesB);
        foreach (string filename in toBeDeleted)
            File.Delete(Path.Combine(pathA, filename));

edited Dec 19 '12 at 08:57

answered Dec 19 '12 at 08:49

Ivan Golović

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2

This answer has three disadvantages. 1. Doesn't work if he wants to search sub-directories(`SearchOption.AllDirectories`) since you're combining with the root directory. 2. Needs to load all into memory first unlike the `EnumerateFiles` methods 3. Is less extensible if OP also wants to include the file-size or other properties. – Tim Schmelter Dec 19 '12 at 09:13
1

OP said he needed to compare file names only. If he's working with .NET version lower than 4, he can't use `EnumerateFiles`. – Ivan Golović Dec 19 '12 at 09:21

score 0 · Answer 4 · answered Dec 19 '12 at 08:51

 string[] FolderAFiles = Directory.GetFiles(@"Path");
            string[] FolderBFiles = Directory.GetFiles(@"BPath");
            foreach (string Files in FolderAFiles)
            {
                if (FolderBFiles.Contains(Files))
                {
                    File.Delete(Files);
                }
            }

Try this

score 0 · Answer 5 · answered Dec 19 '12 at 08:55

0

Here's one another solution.

var filesInB = System.IO.Directory.GetFiles("FolderB");
Array.ForEach(System.IO.Directory.GetFiles("FolderA"), delegate(string fileName){
    if (filesInB.Contains(fileName)) System.IO.File.Delete(fileName);
});

answered Dec 19 '12 at 08:55

sohail.hussain.dyn

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Find the difference of two folders and delete files

5 Answers5