Check out example codes for "load information with txt file to uwp c#". It will help you in understanding the concepts better.

Code Example 1

private async Task AddTextToFile(String textToSave)
    var appFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
    var file = await appFolder.CreateFileAsync("exposure.txt", 
    await Windows.Storage.FileIO.AppendTextAsync(file, textToSave + Environment.NewLine);
    // Look in Output Window of Visual Studio for path to file
    System.Diagnostics.Debug.WriteLine(String.Format("File is located at {0}", file.Path.ToString()));

private async void Button_Click(object sender, RoutedEventArgs e)
    await AddTextToFile(String.Format("MinimumExposure {0}", DateTime.Now.Millisecond.ToString()));

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