Download File Cabinet Image with C#

Howdy, I am trying to download an image from the file cabinet with C#. 

I can download the file but am missing on how to get that response to a particular file, right now it says it downloads successfully, but no image is saved on the computer. 

With a good internal id entered it reports success, with a bad internal id it reports not download.

Here's the code;

            listBox1.Items.Add("logging in");
            Status status = service.login(passport).status;
            listBox1.Items.Add("Attemptng to download");

            RecordRef fileRef = new RecordRef();
            fileRef.internalId = txtImage.Text; //File internal id
            fileRef.typeSpecified = true;
            fileRef.type = RecordType.file;