Searching for List of Substrings for a String in C#

Question

I have a list of filenames:

 List<string> FileList = new List<string>();
 FileList.Add("c:\fn1.rpt");
 FileList.Add("c:\fn2wxy.txt");
 FileList.Add("c:\fn3.pdf");

I have a list of candidates for deletion:

List<string> DeleleList = new List<string>();
DeleteList.Add("fn2")

I have a loop that loops through the file names and I am looking for the correct expression that basically figures out if the file name fragment in the DeleteList matches the current file. In this case, we would delete c:\fn2.txt only. I can iterate the list but it seems as though there must be a Lambda expression somewhere beyond my IQ.

Any help or advice would be greatly appreciated.

Tim Schmelter · Accepted Answer · 2018-02-08 14:29:01Z

3

You should not search substrings but use System.IO.Path.GetFileNameWithoutExtension.

For example with LINQ (keep only those names which don't appear in the DeleteList):

fileNames = fileNames
  .Where(n => !DeleteList.Contains(System.IO.Path.GetFileNameWithoutExtension(n)))
  .ToList()

If you want to ignore the case, so treat fn2 and FN2 equal, use:

.Where(n => !DeleteList.Contains(System.IO.Path.GetFileNameWithoutExtension(n), StringComparer.OrdinalIgnoreCase))

edited Feb 8, 2018 at 14:29

answered Feb 8, 2018 at 14:22

Tim Schmelter

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2 Comments

Anderson Pimentel Over a year ago

In case the OP need it, one can make it case insensitive using .Contains(System.IO.Path.GetFileNameWithoutExtension(n), StringComparer.OrginalIgnoreCase).

Missy Over a year ago

Now this is a way bigger thought than I originally had but why the heck not? Seriously -- I wasn't going for the whole directory - just the array of file names. I'll check it out. I am looking for substrings -- kind of like wildcards. Starts with FN2 -- could be FN2i928340983.xyz.

Marius Bughiu · Accepted Answer · 2018-02-08 14:47:19Z

2

Assuming you have the file name in a variable called fileName, then:

if you want an exact match, then just use Contains:

if (DeleteList.Contains(fileName))

if you want a partial match

if (DeleteList.Any(fileToDelete => fileToDelete.Contains(fileName)))

Instead of Contains you can also use StartsWith or EndsWith.

Edit: I'm assuming your complete code should look like this:

foreach (filename in FileList)
{
   if (DeleteList.Any(fileToDelete => fileToDelete.Contains(fileName)))
   {
       // delete file
   }
}

Though, as others have mentioned, matching on strings like this is not necessarely the best approach. Also, it would probably more intuitive to create a list of files to delete (matching existing files) and iterate through that as a final step and delete the files; like so:

var filesToDelete = FileList.Where(f => DeleteList.Any(df => df.Contains(System.IO.Path.GetFileNameWithoutExtension(f), StringComparer.OrginalIgnoreCase)));
foreach (var filePath in filesToDelete)
{
    //delete file
}

edited Feb 8, 2018 at 14:47

answered Feb 8, 2018 at 14:24

Marius Bughiu

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3 Comments

Missy Over a year ago

I clarified my question. I'm not able to get your answer to work so maybe with my additional comments, I could do it.

Marius Bughiu Over a year ago

Did you manage to get this working after the update to my answer? & what exactly wasn't working with the original answer?

Missy Over a year ago

Sorry it has taken me so long to get back to you. Originally, it wasn't finding the file fragments. I will test this out this weekend. I appreciate your help.

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