c# - Deleting files in use

Question

I created a simple program to delete temporary files in C# (for fun, not a major project) and am running into locked files (in use) issues. How do you normally either exclude those files? For reference I am receiving the error:

The process cannot access the file 'ExchangePerflog_8484fa31c65c7a31cfcccd43.dat' because it is being used by another process.

Code:

static void Main(string[] args)
    {
        string folderPath = string.Empty;
        folderPath = System.Environment.GetEnvironmentVariable("temp");
        deleteFilesInDirectory(folderPath);
    }

    public static void deleteFilesInDirectory(string folderPath) 
    {

        try
        {
            var dir = new DirectoryInfo(folderPath);
            dir.Attributes = dir.Attributes & ~FileAttributes.ReadOnly;
            dir.Delete(true);
            MessageBox.Show(folderPath + " has been cleaned.");
        }
        catch (System.IO.IOException ex)
        {
            MessageBox.Show(ex.Message); 
            return;

        } 
    }     

Answer 1

Description

There is no way to delete a file that is currently in use by another process. But you can wait till the file is not locked.

Check in a while loop till the file is unlocked with this method

protected virtual bool IsFileLocked(FileInfo file)
{
    FileStream stream = null;

    try
    {
        stream = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
    }
    catch (IOException)
    {
        //the file is unavailable because it is:
        //still being written to
        //or being processed by another thread
        //or does not exist (has already been processed)
        return true;
    }
    finally
    {
        if (stream != null)
            stream.Close();
    }

    //file is not locked
    return false;
}

Sample

FileInfo file = new FileInfo("PathToTheFile");
while (IsFileLocked(file))
    Thread.Sleep(1000);
file.Delete();

Update

If you want to skip locked files you can do this.

//
var dir = new DirectoryInfo(folderPath);
foreach(var file in dir.GetFiles()) {
    try
    {
        file.Delete();
    }
    catch (IOException)
    {
        //file is currently locked
    }
}