C# How can I loop through a list string and compare values

Question

I am new to C# and have a project where I have a List String and have to filter some images out with certain extensions . This is my code

// App Config
<add key="FilterImages" value=".jpg ,.gif"/>

List<string> _FilterList = new List<string>();
string[] FilterList = ConfigurationManager.AppSettings["FilterImages"].ToString().Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
foreach (string s in FilterList)
{
    _FilterList.Add(s.Trim().ToLower());
}

var files = newFiles.ListDirectory(".");
foreach (var f in files)
{
    // Here new files come and I can get the file names using
    // f.name ... How can I check for correct extension here   
}

Inside the ForEach loop I would like to use _FilterList and check the file extension of the new files coming in . I can get the file names using f.Name any suggestions would be great

See Path.GetExtension.

Clemens
– Clemens

2018-01-12 14:46:59 +00:00
Commented Jan 12, 2018 at 14:46 — Clemens
– Clemens, Commented Jan 12, 2018 at 14:46

Dmitrii Bychenko · Accepted Answer · 2018-01-12 14:55:22Z

2

First, let's obtain extensions to be filtered out; HashSet<string> seems to be a better collection fo this

HashSet<string> extensions = new HashSet<string>(ConfigurationManager
    .AppSettings["FilterImages"].ToString()
    .Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
    .Select(item => item.Trim()), 
  StringComparer.OrdinalIgnoreCase); // ".GIF" should be treated as ".gif"

Then we can start checking files:

var files = newFiles.ListDirectory(".");

foreach (var f in files) {
  // if "f" is FileInfo we can use f.FullName
  // if "f" is string then put just f, not f.FullName 
  if (extensions.Contains(Path.GetExtension(f.FullName))) {
    // file has a correct extension 
  } 
}

answered Jan 12, 2018 at 14:55

Dmitrii Bychenko

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Comments

Ehsan Ullah Nazir · Accepted Answer · 2018-01-12 14:58:24Z

2

Try some thing like this , Just look for file extension in your FilterList. This may not compile but its an idea how to look for valid file extension.

foreach (var f in files)
{
    if(_FilterList.Contains(Path.GetExtension(f.FileName))
    {
       //Do your stuff
    }
}

Or you can use Linq

 var allowedFiles =  files.Where(p => _FilterList.Any(l => p.Contains(l)).ToList();

edited Jan 12, 2018 at 14:58

answered Jan 12, 2018 at 14:53

Ehsan Ullah Nazir

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1 Comment

Christopher Over a year ago

Would have been my solution too. However there are some caveeats: Case Sensitivty is a thing. And as foreach uses a Enumerator under the hood, you can not modify the collection. So 'your stuff' can not be a Remove operation on files.

GGO · Accepted Answer · 2018-01-12 14:55:02Z

1

First, you can factorize your code using LinQ to :

var _FilterList = ConfigurationManager.AppSettings["FilterImages"].ToString()
     .Split(',')
     .Select(p => p.Trim().ToLower())
     .ToList();

var files = newFiles.ListDirectory(".");

And getting Filtered files path with :

var acceptedFiles = files.Where(p => _FilterList.Any(l => p.Contains(l)).ToList();
var unAcceptedFiles = files.Where(p => !_FilterList.Any(l => p.Contains(l)).ToList();

answered Jan 12, 2018 at 14:55

GGO

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