How to force delete a file used by another process in Asp.net core

Question

I'm working on an ASP.NET Core 5 project. I have this action method:

public async Task<IActionResult> CreateV3EnterCheckFile(IFormFile MarksFile)
{
    var filesCount = Directory.GetFiles("Uploads").Length;

    string path = Path.Combine("Uploads", filesCount + 1 + ".xlsx");

    await MarksFile.SaveToAsync(path);

    var xlImporter = new XLImporter();
    var importedData = await xlImporter.ImportSheetAsync(path, 0);

    var r = (from x in importedData select new { ID = x[0], StudentId = x[1] }).ToList();

    System.IO.File.Delete(path);

    return View();
}

I tried to get IFormFile uploaded file by the user to save it on the server and querying it using one of my projects (that uses LinqToExcel library).

I am querying the data and everything is perfect I still have just one problem it is this line of code:

System.IO.File.Delete(path);

It throws an exception and the message is I can't delete that file because it is still being used by another process.

I'm very sure that the process is related to the LinqToExcel library.

More details :

SaveToAsync is an extension method created by me that is its definition

 public static Task SaveToAsync(this IFormFile file, string pathToSaveTo)
        {
            return Task.Factory.StartNew(() =>
            {
                using (Stream fileStream = File.Open(pathToSaveTo, FileMode.Create, FileAccess.ReadWrite, FileShare.None))
                {
                    file.CopyTo(fileStream);
                }
            });
        }

Please - is there any way or method or solution to delete this file even if it is being used by another process?

Massive thanks in advance.

You should be sure which process is using your file instead of guessing. Forcing the delete feels like a workaround — RoQuOTriX, Aug 07 '21 at 10:12
Ok can you provide me a method to know which process exactly use the file ? — JOCKH, Aug 07 '21 at 10:15
I think you can use the handle.exe of windows to find it out. Maybe also parse the output from your program suggested in this question: https://stackoverflow.com/questions/317071/how-do-i-find-out-which-process-is-locking-a-file-using-net — RoQuOTriX, Aug 07 '21 at 10:18

score 1 · Answer 1 · answered Aug 07 '21 at 10:21

1

Based on the source code of ExcelQueryFactory (https://github.com/paulyoder/LinqToExcel/blob/master/src/LinqToExcel/ExcelQueryFactory.cs) I would try the following:

ExcelQueryFactory has a ReadOnly Property. For read only access (if applicable) I would set it to true when creating the instance.
More important: IExcelQueryFactory implements IDisposable, so you can (should) use a using block:

using (var excelFile = new ExcelQueryFactory(pathToExcelFile) {ReadOnly = true})
{
    // Do your work.
}

Of course you can use using var ..., but if you need a more reduced scope, the "old" using syntax allows more control.

answered Aug 07 '21 at 10:21

Michael

1,166
5
4

Hmm, instead of creating a new Task in SaveToAsync you can use *await file.CopyToAsync()*. Try to delete the file after calling MarksFile.SaveToAsync(). This should be possible. – Michael Aug 07 '21 at 11:05
I tried to delete the file after saving and deleted fine – JOCKH Aug 07 '21 at 13:28

Pritom Sarkar · Answer 2 · 2021-08-08T06:28:06.847

I assumed that your Uploads folder is under webroot.

You can try this:-

 public YourControllerName(IHostingEnvironment he) //input parameter
        {
            
            _he = he;
        }

public async Task<IActionResult> CreateV3EnterCheckFile(IFormFile MarksFile)
{
try 
{ 
    var filesCount = Directory.GetFiles("Uploads").Length;
    
    string contentRootPath = _he.ContentRootPath;

    string path = Path.Combine(contentRootPath +"\\Uploads", filesCount + 1 + ".xlsx");
   

    await MarksFile.SaveToAsync(path);

    var xlImporter = new XLImporter();
    var importedData = await xlImporter.ImportSheetAsync(path, 0);

    var r = (from x in importedData select new { ID = x[0], StudentId = x[1] }).ToList();

    //System.IO.File.Delete(path);

   if (File.Exists(path))
    { 
        File.Delete(path);
    }
    else
    {
        Debug.WriteLine("File does not exist.");
    } 

    return View();
}  

 catch(Exception e) 
 { 
     Console.WriteLine(e); 
 }

Or you can try another process:-

try
{
 System.GC.Collect(); 
 System.GC.WaitForPendingFinalizers(); 
 System.IO.File.Delete(path);
}
catch(Exception e){
}
}

Or this:-

 if (System.IO.File.Exists(path))
        {
            try
            {
                System.GC.Collect();
                System.GC.WaitForPendingFinalizers();
                System.IO.File.Delete(path);

            }
            catch (Exception e) { }
        }

it should resolve your issue I hope. by the way, if your Upload folder is not under the webroot path. you can find your path using your process.

How to force delete a file used by another process in Asp.net core

2 Answers2