uwp streamwriter System.UnauthorizedAccessException

Question

Hi I'm trying to create a txt file in UWP but I'm getting this error: System.UnauthorizedAccessException : Access to the path......

When I use the code in a Console App it works fine but not in UWP. I have tried 3 locations to create the txtfile. AppData folder, usb stick, project folder

Here is the code:

private void TextMethod()
{
    //string file = @"E:\Logfiles\test.txt";
    //string file = @"C:\Users\deeja\source\repos\UwpTxtTest\UwpTxtTest\bin\x86\Debug\test.txt";
    string file = @"C:\Users\deeja\AppData\test.txt";

    if (!File.Exists(file))
    {
        try
        {
            using (StreamWriter sw = new StreamWriter(file, true))
            {
                sw.WriteLine("Hello");
                sw.WriteLine();
                Debug.WriteLine("File created");
            }
        }
        catch (Exception e)
        {
            Debug.WriteLine("Error = " + e);
        }
    }
    else Debug.WriteLine("File already exists");
}
  

Answer 1

If you want to access the file with path in UWP platform, you need to use Windows Storage Api, and enable broadFileSystemAccess capability then enable app access the file system in the Setting page (Setting -> Privacy -> File System - >Choose which apps can access your file system). I have edit code sample below.

private async void TextMethod()
{
    //string file = @"E:\Logfiles\test.txt";
    //string file = @"C:\Users\deeja\source\repos\UwpTxtTest\UwpTxtTest\bin\x86\Debug\test.txt";
    string file = @"C:\Users\minghaoz\AppData\test.txt";
    try
    {
        var textFile = await StorageFile.GetFileFromPathAsync(file);
        if (file != null)
        {
            using (var outputStream = await textFile.OpenStreamForWriteAsync())
            {
                using (var sw = new StreamWriter(outputStream))
                {
                    sw.WriteLine("Hello");
                    sw.WriteLine();
                    Debug.WriteLine("File created");
                }
                outputStream.Dispose();
            }
        }

    }
    catch (Exception e)
    {
        Debug.WriteLine("Error = " + e);
       
        if (e.Message.Contains("0x80070002"))
        {
            var savePicker = new FileSavePicker();
            savePicker.FileTypeChoices.Add("Plain Text", new List<string>() { ".txt" });
            savePicker.SuggestedFileName = "test";
            savePicker.SuggestedStartLocation = PickerLocationId.ComputerFolder;
            StorageFile newFile = await savePicker.PickSaveFileAsync();
            if (newFile != null)
            {
                CachedFileManager.DeferUpdates(newFile);
                // write to file
                using (var outputStream = await newFile.OpenStreamForWriteAsync())
                {
                    using (var sw = new StreamWriter(outputStream))
                    {
                        sw.WriteLine("Hello");
                        sw.WriteLine();
                        Debug.WriteLine("File created");
                    }
                    outputStream.Dispose();
                }
                FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(newFile);
                if (status == FileUpdateStatus.Complete)
                {

                }
                else
                {

                }
            }
            else
            {

            }
        }
    }
}

For more please refer File access permissions document.