download a file from asp.net api in xamarin form? [duplicate] - asp.net

Question

I am trying to save a file to the client's machine. I want to require the client to pick the location of the download.
I have endpoint of the REST service which returns the file to be downloaded. I am trying to set up the code to download the file thats returned from the service with save as dialog.
var Url = "https://randomaddresss/v5/invoices/{" + InvoicesId + "}/getpdfbyid";
HttpResponse response = HttpContext.Current.Response;
response.ClearContent();
response.Clear();
response.ContentType = "application/pdf";
response.AddHeader("Content-Disposition", "attachment; filename=" + InvoicesId + ".pdf;");
response.TransmitFile(Url);
response.Flush();
response.End();
The error thats returned is on the line response.TransmitFile(Url); :
'https:/randomaddresss/v5/invoices/2131231231231312/getpdfbyid'
is not a valid virtual path.

Answer 1

HttpResponse.TransmitFile expects a file path, not a URL.
You will need to download the file first, then write to the response stream.
Here's an example using HttpClient:
using var invoiceResponse = await httpClient.GetAsync(Url);
using var invoiceStream = await invoiceResponse.Content.ReadAsStreamAsync();
invoiceStream.CopyTo(response.OutputStream);
response.ContentType = "application/pdf";
response.AddHeader("Content-Disposition", "attachment; filename=" + InvoicesId + ".pdf;");

Answer 2

JS:
function downloadPdfInvoice(iId) {
$.ajax({
url: '/api/DownloadInvoice?Invoice=' + iId,
type: 'get',
success: function (response, status) {
if (response) {
var link = document.createElement('a');
link.href = "data:application/octet-stream;base64," + response.Data;
link.target = '_blank';
link.download = iId + '.pdf';
link.click();
}
},
});
}
CS:
[HttpGet]
public ApiResponse DownloadInvoiceAsync(string InvoicesId)
{
try
{
String Url = "https://test/{" + InvoicesId + "}/getpdfinvoice";
HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create(Url);
var resp = fileReq.GetResponse();
Stream input = resp.GetResponseStream();
byte[] data = input.ReadAsBytes();
return new ApiResponse(true, "Downloadet til skrivebordet.", data);
}
catch (Exception ex)
{
Logger.Warn(MethodBase.GetCurrentMethod().DeclaringType,
string.Format("DownloadInvoice Exception {0}", ex.Message));
throw ex;
}
}