is returning stream considered anti pattern in web api? - asp.net-web-api

Question

I am from the old world that think webapi should return a strong typed object and let json serialization return data.
However, recently we got this requirement:
We have a sql table which has more than 500 columns.
The customer always want to return all the columns.
Our c# code does nothing other than reading the SqlDatareader, convert the reader to a c# object and return result.
In this case, wouldn't better to do this (example copied from another stackoverflow post). Basically just return a stream? Does returning a stream still considered to be anti-pattern?
public HttpResponseMessage SomeMethod(List<string> someIds)
{
HttpResponseMessage resp = new HttpResponseMessage();
resp.Content = new PushStreamContent(async (responseStream, content, context) =>
{
await CopyBinaryValueToResponseStream(responseStream, someIds);
});
return resp;
}
private static async Task CopyBinaryValueToResponseStream(Stream responseStream, int imageId)
{
// PushStreamContent requires the responseStream to be closed
// for signaling it that you have finished writing the response.
using (responseStream)
{
using (SqlConnection connection = new SqlConnection(connectionString))
{
await connection.OpenAsync();
using (SqlCommand command = new SqlCommand("SELECT 500 columns FROM [StupidWideTable] WHERE ....", connection))
{
.....
using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess))
{
if (await reader.ReadAsync())
{
if (!(await reader.IsDBNullAsync(0)))
{
using (Stream data = reader.GetStream(0))
{
// Asynchronously copy the stream from the server to the response stream
await data.CopyToAsync(responseStream);
}
}
}
}
}
}
}// close response stream
}

Answer 1

Does returning a stream still considered to be anti-pattern?
Well, that depends on what you want to do. For example, if you want to return a 500 if the SQL server fails partway through, then you shouldn't return a stream.
Streaming results works fine on ASP.NET, but it's important to note that all headers (including the response status code) are sent before the stream begins. So you'll send an immediate 200 when you start streaming the result, and if there's an error later on there's no way to go back in time and change that to a 500. Or add some kind of Continue header.
In other words, yes it's supported; but you lose all the benefits of model binding, content negotiation, exception handlers, etc., because you're bypassing that whole pipeline.