HttpClient - Download file size before downloading

Question

I am uploading files with a progress bar. I am using IAsyncOperationWithProgress for this problem, specifically this code . This works well, but I only get the number of bytes that were received / loaded. But I need to calculate the percentage to display progress. This means that I need to know the total number of bytes at the beginning of the download, and I have not found a way to do this efficiently.

The following code enables progress reports. I tried to get the length of the stream using responseStream.Length , but with the error "This stream does not support search operations." was cast.

static async Task<byte[]> GetByteArratTaskProvider(Task<HttpResponseMessage> httpOperation, CancellationToken token, IProgress<int> progressCallback)
        {
            int offset = 0;
            int streamLength = 0;
            var result = new List<byte>();

            var responseBuffer = new byte[500];

            // Execute the http request and get the initial response
            // NOTE: We might receive a network error here
            var httpInitialResponse = await httpOperation;

            using (var responseStream = await httpInitialResponse.Content.ReadAsStreamAsync())
            {
                int read;

                do
                {
                    if (token.IsCancellationRequested)
                    {
                        token.ThrowIfCancellationRequested();
                    }

                    read = await responseStream.ReadAsync(responseBuffer, 0, responseBuffer.Length);

                    result.AddRange(responseBuffer);

                    offset += read;
                    // here I want to send percents of downloaded data
                    // offset / (totalSize / 100)
                    progressCallback.Report(offset);

                } while (read != 0);
            }

            return result.ToArray();
        }

, ? - HttpClient? BackgroundDownloader, . .

Answer 1

Content-Length, , httpInitialResponse.Content.Headers. (.. "Content-Length" )

, , :

int length = int.Parse(httpInitialResponse.Content.Headers.First(h => h.Key.Equals("Content-Length")).Value.First());

( , Content-Length , )

:

static async Task<byte[]> GetByteArrayTaskProvider(Task<HttpResponseMessage> httpOperation, CancellationToken token, IProgress<int> progressCallback)
{
    int offset = 0;
    int streamLength = 0;
    var result = new List<byte>();

    var responseBuffer = new byte[500];

    // Execute the http request and get the initial response
    // NOTE: We might receive a network error here
    var httpInitialResponse = await httpOperation;
    var totalValueAsString = httpInitialResponse.Content.Headers.SingleOrDefault(h => h.Key.Equals("Content-Length"))?.Value?.First());
    int? totalValue = totalValueAsString != null ? int.Parse(totalValueAsString) : null;

    using (var responseStream = await httpInitialResponse.Content.ReadAsStreamAsync())
    {
       int read;
       do
       {
           if (token.IsCancellationRequested)
           {
              token.ThrowIfCancellationRequested();
           }

           read = await responseStream.ReadAsync(responseBuffer, 0, responseBuffer.Length);
           result.AddRange(responseBuffer);

           offset += read;
           if (totalSize.HasValue)
           {
              progressCallback.Report(offset * 100 / totalSize);
           }
           //for else you could send back the offset, but the code would become to complex in this method and outside of it. The logic for "supports progress reporting" should be somewhere else, to keep methods simple and non-multi-purpose (I would create a method for with bytes progress and another for percentage progress)
       } while (read != 0);
    }
    return result.ToArray();
}