The Process cannot access the file because it is being created by another process in vb.net

Question

I am using FilesystemWatcher to look for newfile in the directory. The file type of investigation is .blf. It is being created of size almost 10MB (not constant but around/almost figure) Once the file is created and being written completely, i want to copy the file into someother folder. But the program immediately starts to copy even when the file is in process of being written and i get the error of "The Process cannot access the file because it is being created by another process" i want to make a condition to check if the file is completly created and then do the copy; Below is my code:

Private Sub Fsw1_Created(ByVal sender As Object, ByVal e As System.IO.FileSystemEventArgs) Handles Fsw1.Created
    ListBox2.Items.Add("File- " & e.FullPath.ToString & " created at: " & System.DateTime.Now)
    Dim blffolder As String = String.Format("C:\Users\nha4abt\Desktop\Main\blf_files" + "\{0}", DateTime.Today.ToString("dd-MMM-yyyy"))
    'Check if subfolders exists or not
    If (Not System.IO.Directory.Exists(blffolder)) Then
        System.IO.Directory.CreateDirectory(blffolder)
    End If
    'Repeat steps 1-6
    Dim destPath As String = Path.Combine(blffolder, Path.GetFileName(e.FullPath))
    'System.Threading.Thread.Sleep(1000)
    File.Copy(e.FullPath, destPath, True) 'copy all the files in destination folder 
    ' Compare the two files that are referenced in the textbox controls.
    If (FileCompare(e.FullPath, destPath)) Then
        ListBox1.Items.Add(e.FullPath & "-  is correctly copied :) ") ' put all the names in listbox; Not necessary
        'To Add: make a log file .txt to put the record of all the files that are copied during the process
        Dim strFile As String = String.Format(DestinationDirectory + "\Log_{0}.txt", DateTime.Today.ToString("dd-MMM-yyyy")) 'create a .txt file for log
        Dim texttoappend As String
        Dim timedate As String
        timedate = DateTime.Now
        texttoappend = e.FullPath + vbCrLf + "copied to" & vbCrLf & destPath & vbCrLf & "at" & timedate + vbNewLine & vbCrLf
        File.AppendAllText(strFile, String.Format(texttoappend, Environment.NewLine))
    Else
        MessageBox.Show("Files are not equal.")
        File.Copy(e.FullPath, destPath, True) 'copy again 
    End If

End Sub

I tried to use System.Threading.Thread.Sleep(1000) but couldn't run the program. please guide

Answer 1

I would suggest implementing a Function which checks if the file is still being used by another process and avoid System.Threading.Thread.Sleep(1000).

Original function here

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

    try
    {
        stream = file.Open(FileMode.Open, FileAccess.Read, 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;
}