[U8.1]what is the best way to save a stream to a file?

Question

I can't decide which is better way among the below 2 methods to save a stream to a file in c# 

Method 1: 

int i = 0;
            var bufflist = new List<byte>();
            stream.Position = 0;

            FileSavePicker savePicker = new FileSavePicker();
            savePicker.DefaultFileExtension = ".pdf";
            savePicker.SuggestedFileName = "Final";
            savePicker.FileTypeChoices.Add("PDF", new List<string>() { ".pdf" });
            StorageFile stFile = await savePicker.PickSaveFileAsync();
            myblock.Text = "Saving...";
            if (stFile != null)
            {
                Windows.Storage.Streams.IRandomAccessStream fileStream = await stFile.OpenAsync(FileAccessMode.ReadWrite);
                Stream st = fileStream.AsStreamForWrite();
                st.SetLength(0);

                long length = stream.Length;

                while (i < length)
                {
                    bufflist.Insert(i, Convert.ToByte(stream.ReadByte()));
                    st.WriteByte(bufflist.ElementAt(i));
                    i++;
                }

                await st.FlushAsync();
                st.Dispose();
                fileStream.Dispose();
                myring.IsActive = false;
                myblock.Visibility = Visibility.Collapsed;
            }

Method 2 :

stream.Position = 0;

            FileSavePicker savePicker = new FileSavePicker();
            savePicker.DefaultFileExtension = ".pdf";
            savePicker.SuggestedFileName = filename;
            savePicker.FileTypeChoices.Add("Adobe PDF Document", new List<string>() { ".pdf" });
            StorageFile stFile = await savePicker.PickSaveFileAsync();
            if (stFile != null)
            {
                Windows.Storage.Streams.IRandomAccessStream fileStream = await stFile.OpenAsync(FileAccessMode.ReadWrite);
                Stream st = fileStream.AsStreamForWrite();
                st.SetLength(0);
                st.Write((stream as MemoryStream).ToArray(), 0, (int)stream.Length);
                st.Flush();
                st.Dispose();
                fileStream.Dispose();
            }

Answer 1

Hi kranthi88,

Welcome to the Developing Universal Windows apps forum! 

What type of app are you writing? Please read the sticky posts, especially the Guide to posting: subject line tags and Known Issues for Windows 10 SDK and Tools .

Back to your question, theses two methods are correct, I think the second one should be simple, I will use it.

As a suggestion, you need to make sure that the "stream" variable should not be null:

private async void btnSave_Click(object sender, RoutedEventArgs e)
{
            if (stream != null)
            {
                stream.Position = 0;
                FileSavePicker savePicker = new FileSavePicker();
                savePicker.DefaultFileExtension = ".pdf";
                savePicker.SuggestedFileName = "test";
                savePicker.FileTypeChoices.Add("Adobe PDF Document", new List<string>() { ".pdf" });
                StorageFile stFile = await savePicker.PickSaveFileAsync();
                if (stFile != null)
                {
                    Windows.Storage.Streams.IRandomAccessStream fileStream = await stFile.OpenAsync(FileAccessMode.ReadWrite);
                    Stream st = fileStream.AsStreamForWrite();
                    st.SetLength(0);
                    st.Write((stream as MemoryStream).ToArray(), 0, (int)stream.Length);
                    st.Flush();
                    st.Dispose();
                    fileStream.Dispose();
                }
            }
}

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Answer 2

Are u saying that method 2 is most efficient & fast or is it just a matter of preference ?

Answer 3

Are u saying that method 2 is most efficient & fast or is it just a matter of preference ?

Hi kranthi88,

>>Are u saying that method 2 is most efficient & fast or is it just a matter of preference ?

In my view, the second method is more efficient, there is no need to write Bytes by looping through byte list.

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Answer 4

There's an even faster method.

https://msdn.microsoft.com/en-us/library/system.io.stream.copyto%28v=vs.110%29.aspx

Answer 5

@Franklin Thanx for my concept clearance!!

Answer 6

@mcosmin are u sure that Stream.CopyTo method is faster, efficient & most reliable way to save a stream to a file coz my resultant stream comprises of hundreds of mega bytes, i don't want my app to throw out of memory exception.

Answer 7

Depends on the type of stream, of course!

If your stream is so large, perhaps you should use method 2 you described. But there's always room for testing. Try it out and see if it works.