C# – WPF copy file to the predefined directory

cfilewpf

In a WPF app I need to make it possible for a user to pick a file by the standard Open File Dialog and save it to the predefined folder (user doesn't know where it is) right after the user click OK button on Open File Dialog. Something like of importing a file to the application. I do it in the following way:

        Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();            
        dlg.Filter = "Text documents (.txt)|*.txt"; 
        Nullable<bool> result = dlg.ShowDialog();
        if (result == true)
        {
            string filename = dlg.SafeFileName;
            System.IO.File.Copy(filename, @"E:\TestFolder\" + filename);
            MessageBox.Show("File " + filename + " saved");
        }

Is there a standard way to check if the file already exists before trying to save it and if it is really saved after saving it?

Best Answer

Look at System.File.Exists that should be able to tell you what you need to know.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

Python – How to check whether a file exists without exceptions

If the reason you're checking is so you can do something like if file_exists: open_it(), it's safer to use a try around the attempt to open it. Checking and then opening risks the file being deleted or moved or something between when you check and when you try to open it.

If you're not planning to open the file immediately, you can use os.path.isfile

Return True if path is an existing regular file. This follows symbolic links, so both islink() and isfile() can be true for the same path.

import os.path
os.path.isfile(fname)

if you need to be sure it's a file.

Starting with Python 3.4, the pathlib module offers an object-oriented approach (backported to pathlib2 in Python 2.7):

from pathlib import Path

my_file = Path("/path/to/file")
if my_file.is_file():
    # file exists

To check a directory, do:

if my_file.is_dir():
    # directory exists

To check whether a Path object exists independently of whether is it a file or directory, use exists():

if my_file.exists():
    # path exists

You can also use resolve(strict=True) in a try block:

try:
    my_abs_path = my_file.resolve(strict=True)
except FileNotFoundError:
    # doesn't exist
else:
    # exists

Best Answer

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This is the style that Microsoft tends to use in their examples.

Python – How to check whether a file exists without exceptions

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