Creating a text file on the fly and have it download/save on client side

Question

In our ASP.NET Core 1.1, EF Core 1.1 app we have populated a string with some data from SQL Server and would like to have a text file created out of it on the fly and have a user save/download from the client side.

In old days we used to do it as follows:

List<string> stringList = GetListOfStrings();

MemoryStream ms = new MemoryStream();
TextWriter tw = new StreamWriter(ms);

foreach (string s in stringList) {
    tw.WriteLine(s);
}
tw.Flush();
byte[] bytes = ms.ToArray();
ms.Close();

Response.Clear();
Response.ContentType = "application/force-download";
Response.AddHeader("content-disposition", "attachment; filename=myFile.txt");
Response.BinaryWrite(bytes);
Response.End();

How can that be achieved in ASP.NET Core 1.1? Tried to follow File Providers in ASP.NET Core to no avail.

Answer 1

MemoryReader mr = new MemoryStream();
TextWriter tw = new StreamWriter(mr);

foreach (string s in stringList) {
    tw.WriteLine(s);
}
tw.Flush();

return File(mr, "application/force-download", "myFile.txt")

Or directly write to the response:

HttpContext.Response.Body.WriteAsync(...);

Also viable alternative

TextWriter tw = new StreamWriter(HttpContext.Response.Body);

so you can directly write to the output string, without any additional memory usage. But you shouldn't close it, since it's the connection to the browser and may be needed further up in the pipeline.