For , you must manually manipulate the HttpResponse object to clear existing content and write the binary data directly to the output stream.
: You cannot download files directly via a standard jQuery .ajax() call because AJAX responses are handled by JavaScript, not the browser's download manager. Use a standard link or a submission instead.
Download a Byte Array as a File in Postback - Stack Overflow download file from byte array c# asp.net
: Setting this to attachment ensures the file is saved to the user's disk rather than displayed in the browser window.
[HttpGet] public IActionResult DownloadDocument(int id) { // 1. Get your byte array (from DB, API, or generated) byte[] fileData = GetByteArrayFromDataSource(id); // 2. Define the content type and filename string contentType = "application/pdf"; string fileName = "Report.pdf"; // 3. Return the FileResult // This automatically sets the Content-Disposition header to 'attachment' return File(fileData, contentType, fileName); } Use code with caution. Legacy ASP.NET Web Forms For , you must manually manipulate the HttpResponse
: For very large files, avoid using byte[] as it loads the entire file into the server's RAM. In such cases, consider wrapping your byte array in a MemoryStream and returning a FileStreamResult to improve scalability.
: Ensure you provide the correct ContentType (e.g., image/jpeg or application/octet-stream for generic binary files) so the browser handles the file correctly. Download a Byte Array as a File in
protected void btnDownload_Click(object sender, EventArgs e) { byte[] fileData = GetByteArrayData(); string fileName = "Download.png"; Response.Clear(); Response.ContentType = "image/png"; // Forces the browser to download instead of opening inline Response.AddHeader("Content-Disposition", $"attachment; filename={fileName}"); Response.BinaryWrite(fileData); Response.End(); } Use code with caution. Key Considerations for Implementation