Overwriting the existing file in wp8

Question

i am making an app in which i want to overwrite my file , like i am writing a number in the file and reading but the next time i want to add the new number to the existing file then read it

for writing into the file i am using the code

private async void cross_Click(object sender, RoutedEventArgs e)
{


    byte[] fileBytes = System.Text.Encoding.UTF8.GetBytes(this.ScoreTB.Text.ToCharArray());

    StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;

    var dataFolder = await local.CreateFolderAsync("MyFolder", CreationCollisionOption.OpenIfExists);

    var file = await dataFolder.CreateFileAsync("MyFile.txt", CreationCollisionOption.ReplaceExisting);

    using (var s = await file.OpenStreamForWriteAsync())
    {
        s.Write(fileBytes, 0, fileBytes.Length);
    }
}

and for reading the file

private async void aboutus_Click(object sender, RoutedEventArgs e)
{
    StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;

    if (local != null)
    {
        // Get the DataFolder folder.
        var dataFolder = await local.GetFolderAsync("MyFolder");

        // Get the file.
        var file = await dataFolder.OpenStreamForReadAsync("MyFile.txt");

        // Read the data.
        using (StreamReader streamReader = new StreamReader(file))
        {
            this.Score.Text = streamReader.ReadToEnd();
        }
    }
    else
    {
        MessageBox.Show("No File Created");
    }
}

just help me how to overwrite a existing file in windows phone app development.

Thanks in advance

Answer 1

As I understand, you don't need an overwrite, but append.

1) change ReplaceExisting to OpenIfExists :

  var file = await dataFolder.CreateFileAsync("MyFile.txt", CreationCollisionOption.OpenIfExists );

2) seek to the end of the stream before write:

  using (var s = await file.OpenStreamForWriteAsync())
  {
    s.Seek(0, SeekOrigin.End );
    s.Write(fileBytes, 0, fileBytes.Length);
  }