Develop Reference

connectrion my C# code to external Excel file

I use to Open Excel files from my C# Interop application.
However, I cannot pick up (or get connected to) Excel file, when it is already "in air" - open manualy.
app = new Excel.Application();
foreach(var w in app.Workbooks)
{
if(w.name == "MyFile") found = true; //never ever found
}
Could you please advice How To get connected to MyFile.xlsx, not just Open it?

C# - Kill EXCEL.exe process referencing a particular file

I have a C# application that creates an excel file. But if the file is left open and the app is run the second time, it throws IO exception (since, in the code I am replacing the existing file with new one)
Now, I want to check if the file is open and kill the excel.exe process that is referencing this file.
Is there any way this can be achieved?
Note: There might be several excel files open. I want to close only the process that is using my file.
xlFilePath = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
File.Copy(xlFilePath + "\\file.xlsx", String.Format("{0}\\OutputFile{1}.{2}.xlsx", xlFilePath, DateTime.Now.Year, DateTime.Now.Month), true);
xlFilePath = Path.Combine(xlFilePath, String.Format("{0}\\OutputFile{1}.{2}.xlsx", xlFilePath, DateTime.Now.Year, DateTime.Now.Month));
appl = new Excel.Application(Visible = false);
wbookss = appl.Workbooks;
wbook = wbookss.Open(xlFilePath);
//Excel.Worksheets wsheetss = appl.Worksheets;
wsheet = wbook.Sheets["Sheet1"];
Application_GenerateReport(wsheet);
Clipboard.Clear();
wbook.Close(true);
wbookss.Close();
appl.Quit();
System.Runtime.InteropServices.Marshal.ReleaseComObject(wsheet);
System.Runtime.InteropServices.Marshal.ReleaseComObject(wbook);
System.Runtime.InteropServices.Marshal.ReleaseComObject(wbookss);
System.Runtime.InteropServices.Marshal.ReleaseComObject(appl);
EDIT: The file remains open if there was an exception in the last run. If it is opened by a user, it can be killed by checking the MainWindowTitle property (As suggested by Yeldar).

Another solution could be:
System.Diagnostics.Process.Start("CMD.exe","taskkill /f /im excel.exe");
This line will call command prompt and running the command taskkill.
All opening excel programs will be killed in this way.
Updated: (For one file)
System.Diagnostics.Process.Start("CMD.exe","taskkill /FI "WindowTitle eq Microsoft Excel - filename.xls");

As Excel stores the name of the opened file in its title like this:
Microsoft Excel - filename.xls
You can iterate through the processes and kill the one with the given name:
string filename = "mylist.xls";
var excelProcesses = Process.GetProcessesByName("excel");
foreach (var process in excelProcesses)
{
if (process.MainWindowTitle == $"Microsoft Excel - {filename}") // String.Format for pre-C# 6.0
{
process.Kill();
}
}
Note that:
it will also close all opened files with the same name
it will abandon any changes that user could change
title of Excel window may (or not, not sure, need to check) vary from version to version
However, as I said in comments, it is better to fix causes, but not consequences - just make your program start new Excel application without errors.

Dispose slow on very big filestreams?

I've got this code
string archiveFileName = BuildArchiveFileName(i, null);
string tmpArchiveFileName = BuildArchiveFileName(i, "tmp");
try
{
using (FileStream tmpArchiveMemoryStream = new FileStream(tmpArchiveFileName, FileMode.Create))
{
using (BinaryWriter pakWriter = new BinaryWriter(tmpArchiveMemoryStream))
{
if (i == 0)
{
WriteHeader(pakWriter, pakInfo.Header);
WriteFileInfo(pakWriter, pakInfo.FileList);
uint remainingBytesToDataOffset = pakInfo.Header.DataSectionOffset - CalculateHeaderBlockSize(pakInfo.Header);
pakWriter.Write(Util.CreatePaddingByteArray((int)remainingBytesToDataOffset));
}
foreach (String file in pakInfo.FileList.Keys)
{
DosPak.Model.FileInfo info = pakInfo.FileList[file];
if (info.IndexArchiveFile == i)
{
//Console.WriteLine("Writing " + file);
byte[] fileData = GetFileAsStream(file, false);
int paddingSize = (int)CalculateFullByteBlockSize((uint)fileData.Length) - fileData.Length;
pakWriter.Write(fileData);
pakWriter.Write(Util.CreatePaddingByteArray(paddingSize));
}
}
}
}
}
finally
{
File.Delete(archiveFileName);
File.Move(tmpArchiveFileName, archiveFileName);
}
I've tested this with NUnit on small file sizes and it works perfectly. Then when I tried it on a real life example , that are files over 1 GB. I get in trouble on the delete. It states the file is still in use by another process. While it shouldn't that file should have been disposed of after exiting the using branch. So I'm wondering if the dispose of the filestream is slow to execute and that is the reason I'm getting in trouble. Small note in all my file handling I use a FileStream with the using keyword.

While it shouldn't that file should have been disposed of after exiting the using branch
That's not what it is complaining about, you can't delete archiveFileName. Some other process has the file opened, just as the exception message says. If you have no idea what process that might be then start killing them off one-by-one with Task Manager's Processes tab. That being your own process is not entirely unusual btw. Best way is with SysInternals' Handle utility, it can show you the process name.
Deleting files is in general a perilous adventure on a multi-tasking operating system, always non-zero odds that some other process is interested in the file as well. They ought to open the file with FileShare.Delete but that's often overlooked.
The safest way to do this is with File.Replace(). The 3rd argument, the backup filename, is crucial, it allows the file to be renamed and continue to exist so that other process can continue to use it. You should try to delete that backup file at the start of your code. If that doesn't succeed then File.Replace() cannot work either. But do check that it isn't a bug in your program first, run the Handle utility.

Show every file in a directory, but don't show files that are currently being copied

I have a function that checks every file in a directory and writes a list to the console. The problem is, I don't want it to include files that are currently being copied to the directory, I only want it to show the files that are complete. How do I do that? Here is my code:
foreach (string file in Directory.EnumerateFiles("C:\folder"))
{
Console.WriteLine(file);
}

There's really no way to tell "being copied" vs "locked for writing by something". Relevant: How to check for file lock? and Can I simply 'read' a file that is in use?
If you want to simply display a list of files that are not open for writing, you can do that by attempting to open them:
foreach (string file in Directory.EnumerateFiles("C:\folder"))
{
try {
using (var file = file.Open(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite) {
Console.WriteLine(file);
}
} catch {
// file is in use
continue;
}
}
However -- lots of caveats.
Immediately after displaying the filename (end of the using block) the file could be opened by something else
The process writing the file may have used FileShare.Read which means the call will succeed, despite it being written to.
I'm not sure what exactly you're up to here, but it sounds like two processes sharing a queue directory: one writing, one reading/processing. The biggest challenge is that writing a file takes time, and so your "reading" process ends up picking it up and trying to read it before the whole file is there, which will fail in some way depending on the sharing mode, how your apps are written, etc.
A common pattern to deal with this situation is to use an atomic file operation like Move:
Do the (slow) write/copy operation to a temporary directory that's on the same file system (very important) as the queue directory
Once complete, do a Move from the temporary directory to the queue directory.
Since move is atomic, the file will either not be there, or it will be 100% there -- there is no opportunity for the "reading" process to ever see the file while it's partially there.
Note that if you do the move across file systems, it will act the same as a copy.

There's no "current files being copied" list stored anywhere in Windows/.NET/whatever. Probably the most you could do is attempt to open each file for append and see if you get an exception. Depending on the size and location of your directory, and on the security setup, that may not be an option.

There isn't a clean way to do this, but this... works...
foreach (var file in new DirectoryInfo(#"C:\Folder").GetFiles())
{
try
{
file.OpenRead();
}
catch
{
continue;
}
Console.WriteLine(file.Name);
}

what process is preventing my file from getting deleted in C#

I have a C# single thread application that creates a file. Uses that file and then deletes it. Some times the app has trouble deleting that file. The error I get is:
"The process cannot access the file --file path and file name-- because it is being used by another process."
How can I find out what process has a hold on this file and how can I make that process to let go so that the file can be deleted.

This thing rocks for that very "gotcha".
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx
Process Monitor v3.05
It has a "Filter" submenu so you can fine tune it to the file that is locked.

You need to post the relevant code so we can see.
It is however always important to make sure that your app close the file that it has opened.
usually something like this will ensure that:
using(var f = File.OpenRead("myfile")) {
...
}
or the equivalent:
try {
var f = File.OpenRead("myfile");
} finally {
f.close()
}

Make sure that you are closing file before delete.
if you are using StreamWriter class make sure that you are closing with its variable
Ex. StreamWriter sw = new StreamWriter();
// some writing operation
sw.Close();