How to Prevent 'Cannot copy the file, because it's used by another process' Errors When Copying Files?

Ensuring Completion of File Writing before Copying

When working with files in multiple directories, it's crucial to ensure that files are fully written before attempting to copy them. This prevents the "Cannot copy the file, because it's used by another process" error.

In the code provided, a FileSystemWatcher is created to monitor file creation events in a specified directory. When a new file is created, an event handler copies it to another directory. However, when copying larger files, the issue arises due to premature copying, resulting in the aforementioned error.

To address this, a workaround is necessary. Consider the following methods:

Method 1:

private 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
        // - being processed by another thread
        // - does not exist (has already been processed)
        return true;
    }
    finally
    {
        if (stream != null)
            stream.Close();
    }

    // file is not locked
    return false;
}

Method 2:

const int ERROR_SHARING_VIOLATION = 32;
const int ERROR_LOCK_VIOLATION = 33;
private bool IsFileLocked(string file)
{
    // check that problem is not in destination file
    if (File.Exists(file) == true)
    {
        FileStream stream = null;
        try
        {
            stream = File.Open(file, FileMode.Open, FileAccess.ReadWrite, FileShare.None);
        }
        catch (Exception ex2)
        {
            int errorCode = Marshal.GetHRForException(ex2) & ((1 << 16) - 1);
            if ((ex2 is IOException) && (errorCode == ERROR_SHARING_VIOLATION || errorCode == ERROR_LOCK_VIOLATION))
            {
                return true;
            }
        }
        finally
        {
            if (stream != null)
                stream.Close();
        }
    }
    return false;
}

These methods can be utilized to determine if a file is locked before attempting to copy. This ensures that the copy operation occurs only when the file is fully written, eliminating the "Cannot copy the file, because it's used by another process" error.

The above is the detailed content of How to Prevent 'Cannot copy the file, because it's used by another process' Errors When Copying Files?. For more information, please follow other related articles on the PHP Chinese website!